胎体在母体内发育需（以受精龄计算）多少周？
参考答案：
胎体在母体内发育需38周。
.After boarding the plane, I found my seat _____ by a police officer, wondering whether I got the wrong flight.
A．occupied
B．conquered
C．possessed
D．owned
下列为常见水果的pH，呈碱性的是
A．柿子pH=8.5
B．菠萝pH=5.1
C．苹果pH=4.1
D．杨梅pH=2.5
