Natural Selection Has Been Working on Most Organisms for a Really

Natural selection has been working on most organisms for a really long time, so why isn't everything perfectly designed to suit the environment by now?

A) Mutations keep messing up the good designs.
B) Natural selection can only select for traits the organism already has, and those are not always perfect for the job they need to do.
C) Natural selection sometimes works to perfect a trait for an upcoming environmental change, so it's not perfect right away, but it should be later on.
D) Natural selection might select the perfect trait but then the organism behaves in some way that makes it not work as well as it could.
E) Sexual reproduction mixes up traits no matter how carefully they get selected initially.