Which sentence uses a colon correctly?

Select one:

AIt can sometimes be difficult to tell lakes from rivers: both are generally made up of fresh water, and they often host the same species of fish.

BIt can sometimes be difficult to tell lakes from rivers, both are generally: made up of fresh water, and they often host the same species of fish.

CIt can sometimes be difficult: to tell lakes from rivers, both are generally made up of fresh water, and they often host the same species of fish.

DIt can sometimes be difficult to tell lakes from rivers, both are generally made up: of fresh water, and they often host the same species of fish.