Question

The teacher came into the classroom, ____ on his face.

Answer 1

The teacher came into the classroom, _with a smile ___ on his face.
老师带着微笑走进教室，这里表示一个伴随的状态，所以这里只能用with，有伴随的意思，答案选A

Answer 2

根据句子意思填 smiling

The teacher came into the classroom ，smiling on his face.
这位老师脸带微笑走进了教室。