Plastic heart valves and other human "spare parts" have __________ many recent developments in surge

题目

Plastic heart valves and other human "spare parts" have __________ many recent developments in surgery.
A) been possible B) become possible
C) been made possible D) made possible

答案

选C,这里出现了recent ,所以用的完成时态.make...possible 使...成为可能,这里把宾语提去当主语了,所以用被动.
祝开心~!