If the number of trees were decreased significantly in this enviornment, describe the effect it would have on at least one biotic and abiotic factor in the picture and why. *

Well I'm not completely sure but I've seen your question 2 times so I'll try.   As I know trees and green plants give off oxygen. So if a significant number of trees were taken from the environment I'm guessing the air wouldn't be as fresh, not that we'd be suffering, but there would be less oxygen. (not horrible though). I'm not sure on your biotic and abiotic part though, sorry.

Explanation:

hydrocarbons are organic compounds that contain only hydrogens and carbons. they can be saturated (those which contain only carbon-carbon single bonds) or unsaturated (those which contain carbon-carbon double or triple bonds) in nature. hydrocarbons can undergo several reactions like substitution, elimination etc.  

on substituting one or more hydrogen atoms in hydrocarbon it results in the formation of haloalkane. as the halogen atoms are large compared to the carbon and hydrogen atoms, due to which the molecular weight increases and the bond become polar because of presence electronegative halogen atom and results in the increase in boiling point of the haloalkane.

thus, the correct option is (b) that is the boiling point of the new compound increases on substituting a hydrogen atom with a halogen in a hydrocarbon.