Theory is based on practice and _____ turn serves practice.

问题描述:

Theory is based on practice and _____ turn serves practice.
(A) on (B) in (C) by (D) at
并请说明原因,

选B
真理是建立在实际行动上的,并且反过来服务于时间.
in turn 反过来 的意思.是固定搭配.