问题
选择题
Experts warn that medical waste from hospitals, if properly, may contribute to spreading diseases．
A．not handled
B．not being handled
C．not to be handled
D．not having been handled
答案
A
题目分析：考查非谓语动词。句意：专家警告说，如果医院的医疗垃圾不能正确的处理，可能会导致疾病的蔓延。If 引导的条件句的主语是 medical waste from hospitals ，与handle之间是被动关系，故选A项。
考点 : 考查非谓语动词