家鸽卵细胞指的是 [ ]
A．整个家鸽卵
B．胚盘，卵黄和卵黄膜
C．胚盘
D．卵黄
答案：B
If he can ____________ a little longer,we can get help for him. [ ]
A.hold up
B.hold on
C.keep up
D.keep on
由以下哪条特点可判断某种凝胶为非牛顿流体
A．生物相容性B．水溶性C．假塑性D．耐热性E．表面活性
