The students are too to keep their eyes open in class because of staying up late.A. sleep

问题补充：

The students are too to keep their eyes open in class because of staying up late.

A. sleeping

B. asleep

C. sleep

D. sleepy

答案：

A. sleeping

B. asleep

C. sleep

(答案→)D. sleepy

解析：

试题分析: 句意因为熬夜，学生们在课堂上困得睁不开眼了。Sleep睡觉，asleep醒着的，sleepy困的。Too.+adj+to...太......而不能......,固定句型，故选D。