理论考试合格证由地区管理局颁发并注明考试的专业类别。理论考试合格证有效期为()年。
A、1
B、2
C、3
D、4
参考答案:C
The incident turned him into _____ different person, even if he did not realize it at _____ beginning. [ ]
A. a; a
B. the; the
C. the; a
D. a; the
观察生活中的物品和儿童玩具,哪些是利用弹性势能工作的?