The correct answer is the immune system, more specifically, the thymus gland. The thymus gland, while it produces hormones like thymosin, it is more closely related to the immune system rather than the endocrine system. This is because lymphocytes that go into the thymus gland mature into T lymphocytes that can either be a helper T cell or a cytotoxic T cell, depending on the stimulus.
B.) would be the correct answer
C.
Biotic mean alive, so we can cut off the first 2 easily. Aquatic birds eat frogs, so that one is safe for now. A decrease in something parasitic usually helps the population, so D is out too. The only one left is C.
Answer;
-In the smooth ER
In certain kinds of muscle cells, calcium ions are stored in the smooth ER.
Explanation;
-The smooth endoplasmic reticulum is the part of the endoplasmic reticulum (ER) which does not have ribosomes bound to it, thus not exhibiting the bumpy appearance shown by the rough endoplasmic reticulum.
-The smooth ER is important in the synthesis of lipids, such as cholesterol and phospholipids, which form all the membranes of the organism. In addition it is important for the synthesis and secretion of steroid hormones from cholesterol and other lipid precursors.
