It's high time that we students even harder at our lessons as the national entrance exami

问题补充：

Its high time that we students even harder at our lessons as the national entrance examination is coming nearer.

A. work

B. will work

C. worked

D. have to work

答案：

A. work

B. will work

(答案→)C. worked

D. have to work

解析：考察虚拟语气。固定句式It is time that sb should do sth/过去时；是某人做某事的时候了。句意：因为高考即将来临，是我们学生努力学习的时候了。故C正确。