Answer:
The correct option is;
a) Rotten eggs
Step-by-step 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.