Which process will decrease the level of co2 in the atmosphere?
growing trees
cutting trees
burning trees
increasing the human population

Option A, growing trees

Explanation:

Plant and trees take in carbon dioxide as a part of their respiration process and release oxygen as a by product. Thus, if more and more trees are grown , more and more carbon dioxide will be converted into oxygen. Hence, growing trees will reduce the level of CO2 in the atmosphere

However, cutting and burning trees will lead to release of carbon dioxide into the atmosphere. The respiration system of human being and all other living creatures is opposite to that of trees i.e they take in oxygen and release carbon dioxide.

Hence, the higher the number of human beings, the higher will be the CO2 concentration in atmosphere.

Hence, option A is correct

"d.) carbon dioxide and hydrogen sulfide"