ANS:E - all the above.

During the putrefaction process of sewage, various gases are produced as byproducts of microbial decomposition. These gases can include:

1. Carbon dioxide (CO2): Carbon dioxide is a common byproduct of organic decomposition and microbial respiration during sewage putrefaction.
2. Hydrogen (H2): Hydrogen gas can also be produced during anaerobic decomposition of organic matter in sewage.
3. Ammonia (NH3): Ammonia gas can be released as organic nitrogen compounds break down during sewage putrefaction.
4. Methane (CH4): Methane gas is generated through anaerobic digestion of organic matter by methanogenic bacteria in sewage treatment processes.