原始生殖细胞来源于
A．副中肾管B．原始性腺C．卵黄囊(内胚层)D．中肾管E．尿生殖嵴
参考答案：C
—Could you please tell me something about your travel in Sydney?
— _______!
A．Excuse me.
B．It’s very nice of you to say so.
C．Certainly, I’ll be glad to.
D．No, I don’t like it.
某井没有系统试井资料，但已知周围同层的几口生产井的合理压差都为静压的60％左右，试求该井的合理压差。
