The strong smelling substance added to LPG is:
A. Ethyl mercaptan
B. Ethanol
C. Ethanol
D. Ethyl butane

Hint- In order to deal with this question first we will understand the basic definition of LPG gas then according to the elements comprising LPG, we will check for the correct answer amongst the given options.

Complete answer:
The heavier fraction of LPG is containing propane, butane, pentane etc. may be liquefied under pressure to produce liquefied petroleum gas.
So, LPG gas is basically propane and butane, and it is odorless in its natural state. The smell that you notice when there is a leak is actually the stench of an entirely different agent, called ethyl mercaptan $\left( {{C_2}{H_6}S} \right)$ .This substance is added to the gas when it leaves the main storage terminals.
This substance is added in order to detect its leakage of LPG at the household level in order to save from fire accidents.
Hence, the strong smelling substance added to LPG is ethyl mercaptan.
So, the correct answer is option A.

Note- Liquefied petroleum gas is hydrocarbon which can be, or has been, changed from gas to liquid by applying moderate pressure. Liquefied petroleum gas is stored under pressure to keep the hydrocarbons liquefied at normal atmospheric temperatures. LPG has various uses from household to industries as it has lower pollution level than other fuels at same rate.