As is known to all theory is based on practice and serves practice.A. by chanceB. by tu

问题补充：

As is known to all , theory is based on practice and serves practice.

A. by chance

B. by turn

C. in return

D. in turn

答案：

A. by chance

B. by turn

C. in return

(答案→)D. in turn

解析：短语辨析。by chance偶然；by turn轮流；in return作为回报；in turn轮流，依次，转而，反过来。句意：众所周知，理论以实践为基础，反过来又应用于实践。所以选D。