I think that the answer is C.
Answer:
Dead plant matter
Explanation:
Saprotrophs feed by a process known as absorptive nutrition, in which the nutritional substrate (e.g., dead organism or other nonliving organic matter) is directly digested by a variety of enzymes that are excreted by the saprotroph.
I believe the answer is D.
Systolic pressure is when the ventricles contract.