在迄今为止的半个多世纪里，航天技术飞速发展，人类已将（）多个各种类型的航天器送上太空
A.1000
B.2000
C.3000
D.5000
参考答案：D
She ___ have left school, for her bike is still here. [ ]
A. can't
B. mustn't
C. shouldn't
D. needn, t
人类学习和学生学习之间是一般与特殊的关系。
