The students all looked at me when I told them that they would have one more day off.A.

问题补充：

The students all looked at me when I told them that they would have one more day off.

A. sad

B. sadly

C. happy

D. happily

答案：

A. sad

B. sadly

C. happy

(答案→)D. happily

解析：本题的含义是当我告诉学生们还有一天假期，他们应该都开心地看着我，修饰动词看用使用副词happily，故本题选D。