Rick often does _____ homework at 6:00. [ ]
A. her
B. his
C. my
D. your
答案：B
已知＝1，求＋x－1的值
关于振动沉桩法的特点，说法错误的是( )。
A．设备构造简单 B．适用范围较窄C．所消耗的动力少 D．宜用于黏性土
