Why A and not D

D says that critics have an adequate understanding of the economical and biological impact of commercial plantations. A is correct because of the last paragraph. The passage suggests in line 45 that critics are highly critical of commercial plantations. The author then proceeds his counterargument to the critics by stating in line 47-50 that these plantations are used for economic purposes, which reduces natural forests from being used for economic purposes and has a bonus of allowing those forests to maintain their biodiversity.