As is required by their employer the employees finish the project within this month.A. c

问题补充：

As is required by their employer, the employees finish the project within this month.

A. could

B. shall

C. may

D. should

答案：

A. could

B. shall

C. may

(答案→)D. should

解析：句意：正如雇主的要求,雇员应该在本月内完成该项目。四个情态动词的含义分别是：A. could能够， B. shall应该，C. may可以，D. should应该，从句中用了required，所以主句用should do表示虚拟语气。选D。