There are 31 pairs of spinal nerves in the human body. The spinal nerves are grouped according to where they leave the vertebral column. There are eight pairs of cervical nerves (C1-C8), twelve pairs of thoracic nerves (T1-T12), five pairs of lumbar nerves (L1-L5), five pairs of sacral nerves (S1-S1) and one pair of coccygeal nerves (Co1).

The skin does not merely protect the frog but helps in respiration. Fine blood vessels run throughout the frog's skin; oxygen can pass through the membranous skin, thereby entering directly into the blood. When a frog submerges beneath the water, all its respiration takes place through the skin. Oxygen is obtained directly from the water.

A thermometer is used to measure temperature.

The distance of image from plane mirror is same that of object.

If you live in a place that has lots of snow and ice in the winter, you have probably seen the highway department spreading salt on the road to melt the ice. You may have also used salt on ice when making home-made ice cream. Salt lowers the freezing/melting point of water, so in both cases the idea is to take advantage of the lower melting point. Ice forms when the temperature of water reaches 32 degrees Fahrenheit (0 degrees Celsius). When you add salt, that temperature drops: A 10-percent salt solution freezes at 20؛F (-6؛C), and a 20-percent solution freezes at 2؛F (-16؛C). On a roadway, this means that if you sprinkle salt on the ice, you can melt it. The salt dissolves into the liquid water in the ice and lowers its freezing point.

Materials which are classed as conductors tend to increase their resistivity with an increase in temperature. Insulators however are liable to decrease their resistivity with an increase in temperature.

Wires are of different colours so as to distinguish between live wire, neutral wire and earth wire. They are of three different colours- live wire: red colour neutral wire: black colour earth wire: green colour

A substance with a definite shape and definite volume is called solid.

Humidity is a term for the amount of water vapours in the air, and can refer to any one of several measurements of humidity.

2,8,7 is configuration of chlorine which is a non metal.

According to the definition, there are currently eight planets and five dwarf planets known in the Solar System. Pluto is a dwarf planet.

Our ears are most sensitive to sounds in the frequency range of 3000 Hz - 4000 Hz. Almost nobody hears sounds outside the range of 20 Hz - 20000 Hz.  Sound waves with frequencies less than 20 Hz are called infrasonic waves and sound waves with frequencies higher than 20000 Hz are called ultrasonic waves.

The average period of Halley's Comet's orbit is 76 years.

In current use, the term refers to the coating of steel or iron with zinc. This is done to prevent rusting of the ferrous item. The value of galvanizing stems from the relative corrosion resistance of zinc, which, under most service conditions, is considerably less than those of iron and steel.

As an object in uniform circular motion traverses half of a revolution, its centripetal force does no work, but it transfers a nonzero impulse.

A battery converts chemical energy into electric energy.

The coated end of a match, known as the match head, contains either phosphorus or phosphorus sesquisulfide as the active ingredient and gelatin as a binder. There are two main types of matches: safety matches, which can be struck only against a specially prepared surface.

Potato chips, nuts, tortilla chips and other snack foods have their packaging filled with nitrogen gas to preserve their freshness and extend shelf-life.

The image formed by the eyepiece of a telescope is a virtual image of the real image produced by the objective.

Glucose is the human body's key source of energy, through aerobic respiration, providing approximately 3.75 kilocalories.

Iodine is the non metal with lustrous property.

A gene is a segment in a chromosome found inside the nucleus of a living cell. The traits of an individual, such as the appearance, nature of the voice, resistance to certain diseases etc, coming down from ones ancestry are chemically coded in the genes. They not only contain the recipes for the production of body tissues and enzymes required for respiration and digestion etc,  even the time and the duration for various actions such as growing a beard and producing milk after pregnancy are precisely programmed.

Heating effect of electricity is one of the widely used effects in the world. When electric current is passed through a conductor, it generates heat due to the resistance it offers to the current flow. In iron there is a resistance wire which heats up.

 Rice requires the largest area for cultivation in India.

Sleep is a period of reduced activity. Sleep is associated with a typical posture, such as lying down with eyes closed in humans. Sleep results in a decreased responsiveness to external stimuli.