15 is not a prime number.

Sum of the digits, i.e. 4 + 5 = 9, is not a prime number. Hence, this is the odd one out.

This is the word December, which has 31 days, while all others have 30 days.

Except fingers, all the other given body parts are in pairs, i.e. two in number, but fingers are more than two in number.

 All the digits are not odd in the number unlike others . 

ORCLUO is the word COLOUR, but all the others are names of colours. Hence, this is the correct answer.

Tuberculosis is an air borne disease, while all the othes are insect borne diseases. Cholera is also an insect borne disease.

All the others are  names of cities, while America is a continent.

In RT7 , the letters are not in the order from left to right. S comes after R, which is missing. So, the correct series should be RS7.

In all other options, the second number is the square of the first number except this option. The square of 4 is 16 and not 12.

 Tomato is a fruit so this is the odd one.

Sachin Tendulkar is a crickter, while Aamir khan is an actor.

DF is the odd one because there is one letter between the two letters D and F, while the other options are consecutive. In GH, the two letters G and H are consecutive.

 All the other options have a vowel and two consonants, but in BCD, all the three are consonants.

In this, the three letters are not in proper series; the proper series is UVW.