问题补充：
In winter, it is dangerous to go to school with snow the ground.
A. cover
B. to cover
C. covering
D. covered
答案：
A. cover
B. to cover
(答案→)C. covering
D. covered
解析：考查with的复合结构。with +n+ doing/done/to do,选择动词的形式要看名词和动词之间的关系。snow 与cover 之间是主动关系，“雪覆盖地”所以用covering，所以选C。
