The right answer is B because he doesn't believe that the animals know enough to change.
If you are looking for the conjuction word in there it is yet
The correct answer should be Find the meaning of the word "terminating" in an online dictionary.
Finding it in an online dictionary would be rather easy and quick, while it would also be the most correct since the world does not have a polysemic meaning in this context. Context can be tricky while finding antonyms would not be that useful.
