Questions

It is WATER.

Mumbai has been ranked the world's second most densely populated city with 31,700 people per sq km, by the World Economic Forum (WEF) citing UN Habitat Data. Bangladesh's capital Dhaka topped the list with 44,500 people per sq km. Rajasthan's Kota has been ranked the world's seventh most densely populated city with 12,100 people per sq km.

BIOS in computers stands for Basic Input Output System.

BIOS is a set of computer instructions in firmware which control input and output operations.

Cryogenic Engines find applications in Rocket technology. A cryogenic rocket engine is a rocket engine that uses a cryogenic fuel or oxidizer, that is, its fuel or oxidizer are gases liquefied and stored at very low temperatures. Notably, these engines were one of the main factors of NASA's success in reaching the Moon by the Saturn V rocket.

Amylase, also called Ptyalin, which is capable of breaking down starch into simpler sugars such as maltose and dextrin that can be further broken down in the small intestine is the Enzyme present in Saliva.

Logic is

1st fig : 9x2 + 5 = 23

2nd fig : 6x3 + 4 = 22

3rd fig : Nx4 + 5 = 9 => N = 1.