Another drug that has helped improve people’s health is penicillin, is by many one of t

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

A. which, considered, beingB. that, considering, beenC. that, to consider, being(答案→)D. which, considered, to be解析：考察非限制性定语从句和固定搭配。本题第一空考察的是定语从句，先行词是penicillin，which指代先行词在句中作主语。第二空是固定搭配consider…to be…这是一个被动语态的形式。句意：另外一种能够帮助改善人们健康的药物与是盘尼西林，它被很多人认为是最重要的药物之一。故D正确。

我明天再问问老师，叫他解释下这个问题