Asphixiation is a hazard posed by compressed natural gas (CNG) vehicles and can be detected when you notice this smell a) Rotten Eggs
b)Cinnamon
c)Burning
d)spoiled milk

The correct option is;

a) Rotten eggs

Explanation:

Asphyxiation hazard posed by compressed natural gas (CNG) can be detected when the smell of rotten eggs is noticed

Compressed natural gas is made 90% of the colorless and odorless gas, but highly combustible gas, methane, a gaseous additive known as Mercaptan that has the smell of rotten eggs is added so that a person can become alerted by the smell given off in the system should there be a leak.

The smell of the Mercaptan can be detected as low as when the concentration of the the CNG is 1/16 times the concentration required for the combustion of the CNG.