The operation room in every hospital has to bacteria of any kind.
A. keep free from
B. make it free from
C. be made free from
D. be kept free from
网友回答
A. keep free from
B. make it free from
C. be made free from
(答案→)D. be kept free from
解析：考查固定词组和语态。固定词组free from免受…的伤害；句意：每家医院的手术室要被设成不受任何细菌的影响。根据句意说明使用被动语态。