Radon gas is a source of natural groundwater pollution.

Saudi Arabia is the country in the world to have no cinema theaters.

With the exception of one IMAX theater in Khobar by Khalid, there were no cinemas in Saudi Arabia from 1983 to 2018, although there was occasionally talk of opening movie theaters, and in 2008 conference rooms were rented to show the comedy Mennahi.

The given number series is 2, 16, 3, 81, 4, ?

2

2^4 = 16

3

3^4 = 81

4

4^4 = 256

Hence, the next number is 256.

16/3 = 5.333.. = 5.3

The given 3b - 7 < 32 can be solved as

3b - 7 < 32

3b < 39

b < 13.

Smoke alarms are also necessary in public places like banks, theaters, rest rooms, aeroplanes,...

We know that,

Weight W = mg. That is mass times gravitational force.

In hydrocarbon, the boiling point directly varies with the length of carbon chain. On increasing the number of carbon atom, the boiling point of the compound also increases. Paraffin contains highest number of carbon atoms whereas, ethane is comprised of two carbon atoms.

The decreasing order of boiling point of mention compounds is written as follows:

Paraffin > Octadecane > Hexane > Neohexane > Ethane