如果桩的（）与正常桩的典型导纳曲线有较大出入，则桩身可能有各种缺陷。
参考答案：实测导纳曲线
用所给动词的适当形式填空。
1. He _____ (be) born in 2002.
2. How long did he _____ (hiccup)?
3. I looked carefully but _____ (see) nothing.
4. Mike often _____ (go) swimming when he was young.
5. Mozart _____ (start) writing music when he was four years old.
对象之间通过消息机制实现相互作用与通信，______不是消息的组成部分。
A．基类
B．派生类
C．抽象类
D．用户定义类型
