问题
Another drug that has helped improve people’s health is penicillin, _________ is _________ by many _________ one of the most important medicines.
A:which, considered, being
B:that, considering, been
C:that, to consider, being
D:which, considered, to be
B:that, considering, been
C:that, to consider, being
D:which, considered, to be
正确答案是：
