I need help on this picture

Magnesium is the fourth most abundant mineral in the body and is essential to good health. magnesium is needed for more than 300 biochemical reactions in the body. it maintain normal muscle and nerve function, keep bones strong, keep one’s heart rhythm steady, and supports a healthy immune system. magnesium also regulate blood sugar levels, promotes normal blood pressure, and may play a role in energy metabolism and protein synthesis. doctors and scientists are trying to determine whether magnesium may play a role in preventing and managing disorders such as hypertension, cardiovascular disease, and diabetes. which is the main idea of this paragraph? a. the role of magnesium in human nutrition is being studied intensely. b. magnesium may be related to the body’s metabolism and other healthy functions. c. magnesium appears to contribute to hypertension, cardiovascular disease, and diabetes. d. magnesium and a healthy immune system are separate diseases.

Which of the following best explains why the author chose the compare-and-contrast structure for paragraph 2

Answer this correctly what is the cause and effect