Answer:
a, b, and d are the correct answers
Explanation:
Yes ( my answer is too short, but yes, they can turn from one into the other in process like compression, heating, etc.)
The respiratory usually develops at 12 weeks so i would definitely say breathing starts in this period.
Monocyte/macrophages are two non-specific immune defenses. If you had no skin it would be pretty tough to roll around in the mud without getting an infection. Also, without the WBCs chillin in there to catch anything that happened to break through you would get an infection every time you get a paper cut.
