For this question, I narrowed it down to B and D, and ultimately picked B. Here's my reasoning:
While they are both implied, B is pretty directly implied: forests lead to fewer floods, prevent clogging rivers (lines 6-7). Thus forest make sure water-based transportation is not stymied by a flood or impassable river. This is still a jump--you have to assume the flooding is happening in places where their is ocean/river/lake transport, and/or that rivers are still a viable type of transport (they are, though for us US citizens it might seem foreign since most US rivers are not primarily used to transport people as much as products such as coal).
D is sort of implied but it also seemed riddled with traps-- while line 30 says "especially" rain forest diversity should be preserved, so maybe the "more" is justified and not a comparison trap, we don't know for sure that this is internationally recognized.
I don't know if this is the right reason to discount D, but its many qualifiers sent up a lot of alarms, and B felt safer.