课余体育竞赛根据竞赛进行的空间可分为()
A.校内竞赛和校外竞赛
B、学校运动会和单项运动竞赛
C、综合性比赛和单项竞赛
D、季节竞赛和体育节
参考答案:A
The famous writer _____ one new book in the past two year.[ ]
A. is writing
B. was writing
C. wrote
D. has written
为什么混凝土中掺入适量加气剂可以减少用水量?