Questions

The rungs or the sides of the DNA ladder is made of Deoxyribose, which is a pentose, and a phosphate group are the two molecules together form the two sides of the DNA i.e, A sugar (deoxyribose) and a phosphate.

'Rare earth'(They are all metals)

A Kitten.

A Carpet is the pet which always stays on the floor.

Two series alternate here, with every third number following a different pattern.
In the main series, 4 is added to each number to arrive the next.
In alternate series, 5 is subtracted from each number t arrive the next number.
Here in the main series 
3 + 4 = 7
7 + 4 = 11
11 + 4 = 15
15 + 4 = 19

In alternate series 
24 - 5 = 19
19 - 5 = 14...

The First and Last Indian viceroys of India is C. Raj Gopalachari. 

Chakravarti Rajagopalachari, informally called Rajaji or C.R., was an Indian politician, independence activist, lawyer, writer, historian and statesman. Rajagopalachari was the last Governor-General of India, as India soon became a Republic in 1950.