问题补充:
As is known to all, theory is based on practice and serves practice.
A. in hand
B. in turn
C. in return
D. in exchange
答案:
A. in hand
(答案→)B. in turn
C. in return
D. in exchange
解析:考查词组辨析。In hand在手头,在控制中 in turn轮流,反过来(作用于) in return 作为回报 in exchange 交换 本句意为,众所周知,理论建立在实践的基础之上,反过来服务于实践。