Ultrasonic waves are used in sonography for the mapping of body organs. The Ultrasonic waves that are sent inside the body are reflected from the different parts by creating the echo. They are more useful and less harmful than radiation.

Frequency of microwaves, $\upsilon _m \approx 10^{11}Hz$
Frequency of ultrasonic sound waves,$\upsilon _m \approx 10^5Hz$
$\therefore \, \dfrac{\upsilon _m}{\upsilon _u} = \dfrac{10^{11}}{10^{5}} = 10^6$

Answer is A.

Rhinos have extremely good ears, picking up infra-sound far deeper than the range of human hearing.
Rhinos, can hear down to a frequency of four hertz, whereas even a human baby, with entirely undamaged ears, can normally only pick up sounds as low as 20 hertz. Giraffes and elephants can also hear in this infra-sound range.

Answer is A.

Earthquake produces infra-sound before the main shock wave.Infra-sound is a low-frequency sound. It is sound that is lower in frequency than 20 Hz (hertz) or cycles per second, the normal limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infra-sound, the sound pressure must be sufficiently high. 
Rhinos have extremely good ears, picking up infra-sound far deeper than the range of human hearing.
Rhinos, can hear down to a frequency of four hertz, whereas even a human baby, with entirely undamaged ears, can normally only pick up sounds as low as 20 hertz. Giraffes and elephants can also hear in this infra-sound range.
Hence, we can see some animals get disturbed and start running here and there just before the earthquakes because they can hear infrasonic sound.

The waves below the frequency of 20 Hz are infrasonic waves. So the waves of 5 Hz is also an infrasonic wave.

Sounds having frequency more than 20,000 Hz are called Ultrasonic sound. As this is above the normal hearing range for humans, we cannot hear ultrasonic sound.

A sound of frequency 50,000 hertz can be heard by a dog but not by a man. The waves having frequency between 20Hz-20,000Hz are audible frequency of waves.

This is because the screams are ultra sonic(above 20,000 hertz) which human ear cannot hear.

Ultrasound is used to see what is happening in a nuclear reactor.Ultrasounds and infra sounds are not audible to man.ultrasound have frequency more than
20kHz. Infrasound have frequency below 20Hz

Elephants can communicate using very low frequency sounds, with pitches below the range of human hearing. These low frequency sounds, termed infrasonic sounds, can travel several kilometers, and provide elephants with a private communication channel that plays an important role in elephants complex social life. Their frequencies are as low as the lowest notes of a pipe organ.

Ultrasonic frequency is above audible range means above $20KHz$ and infrasonic frequency is below the audible range which means below $20 Hz$.

The property of ultrasonic waves in manufacturing emulsion for photographic films in its high frequency. The frequency of ultrasonic wave is above $20 KHz$

the audible range of human ear is $20Hz - 20000Hz$

$\displaystyle \lambda = \left ( \frac{330}{20} m - \frac{330}{20 \times 10^3} m \right )$
$=(16.5m - 16.5 mm)$

Answer is B.

Most bats produce echolocation sounds by contracting their larynx (voice box). A few species, though, click their tongues. These sounds are generally emitted through the mouth. Echolocation calls are usually ultrasonic, ranging in frequency from 20 to 200 kilohertz (kHz), whereas human hearing normally tops out at around 20 kHz.
While using echolocation, the bats emit a series of short, high-frequency sounds from their mouths or nostrils that bounce off objects and surfaces and then return to the animals ears. Since high-frequency waves do not diffract, or bend, extensively, these ultrasonic vibrations provide bats with accurate maps of their surroundings. 

An echocardiogram (also called an echo) is a type of ultrasound test that uses high-pitched sound waves that are sent through a device called a transducer. The device picks up echoes of the sound waves as they bounce off the different parts of your heart. These echoes are turned into moving pictures of your heart that can be seen on a video screen.
Hence, the statement is false.

The waves below the frequency of 20 Hz are infrasonic waves. So, the wave of 5 Hz is also an infrasonic wave.

Sound waves are categorized on the basis of their frequency range.

Human beings can normally hear sounds with a frequency between about 20 Hz and 20,000 Hz. Sounds with frequencies below 20 hertz are called infrasound. Infrasound is too low-pitched for humans to hear.

The audible wave length range of human beings in (16.5 mm - 16.5 m)
Hence 1 m is the correct option.

yes , below 20hz frequency sound is infrasonic.

Adult humans can hear from 20Hz to 20000Hz of frequency.

Some of the elephant's vocalizations are infrasonic, and thus are inaudible to humans. The prominence of very low frequencies in the vocalizations is a defining characteristic of all three species of elephants. Sounds are generally considered to be infrasonic if their frequency is less than $20 Hz$ (the lower limit of human hearing). Low frequency sounds travel farther than high frequency ones, which make them ideal for long distance communication.
Hence, Elephants produce infrasonic sound. 

Infra-sound is a low-frequency sound. It is sound that is lower in frequency than $20 \ Hz$ or cycles per second, the normal limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high. The ear is the primary organ for sensing infra-sound, but at higher intensities it is possible to feel infra-sound vibrations in various parts of the body.

Rhinos have extremely good ears, picking up infra-sound far deeper than the range of human hearing.
Rhinos, can hear down to a frequency of four hertz, whereas even a human baby, with entirely undamaged ears, can normally only pick up sounds as low as 20 hertz. Giraffes and elephants can also hear in this infra-sound range.