Question

有一道SAT题 麻烦了

（ One important cause of the medication shortage is when ) healthy people, attempting to vuild up immunity, take medications that are intended to treat illnesses.
改为
A~ One important cause of the medication shortage is that
B~ Most medication shortages are the result of that
C~ Most medication shortages result from when

哪两个不对，麻烦解读一下为什么，谢谢各位高手相助了，有追加

Answer 1

B & C are incorrect.

For B, "result of" must be followed by nouns, e.g. result of bad weather

For C, "result from" must be followed by nouns, e.g., result from bad weather