组合件可以分为：______组合件、______组合件、______组合件。
参考答案：单轴线；平面；立体
The meeting _______ by the time I got there yesterday. [ ]
A. was on
B. has been on
C. had begun
D. has begun
中国园林的三个源头是什么？其中的一个源头囿产生于何时？
