The best answer here is choice B. We can determine this because of the tense used throughout the passage itself. Bearing this in mind, choice B matches the tense perfectly.
Choice A does not work at all because the verb "am" makes no sense in the context of the sentence. The same is true for choice C. The passage is not in present tense, so it cannot be this choice. Choice D could make sense, except that this is in the future tense versus the past tense.
Answer:
any of an order of mammals comprising kangaroos, wombats, bandicoots, opossums, and related animals.
Explanation:
They do not develop a true placenta and that usually have a pouch on the abdomen of the female which covers the teats and serves to carry the young
