The captain commanded that the players their pacesA. should slowB. slowedC. could slowD.

问题补充：

The captain commanded that the players their paces

A. should slow

B. slowed

C. could slow

D. slows

答案：

(答案→)A. should slow

B. slowed

C. could slow

D. slows

解析：考查虚拟语气。动词command后面的宾语从句使用虚拟语气should 动词原形；should可以省略。故A正确。