根据实物图画出相应的电路图并在图中标出通过灯L2中电流的方向和电流表的正负接线柱

能分泌抗体

A．NK细胞
B．B细胞
C．肥大细胞
D．细胞毒性T淋巴细胞
E．浆细胞

—Mrs.Smith didn't come to the meeting, _____?

—No, _____.She was ill.[ ]

A. did he; he didn't            

B. did he; he did

C. didn't she; she didn't        

D. did she; she didn't

245. It is estimated that over 15,000 citizens will ____ the celebration, such a grand occasion once every ten years.

A．join in

B．keep out of

C．keep at

D．take part in

网络层的数据单元称为数据帧。（）

十字花科蔬菜黑腐病在叶部病斑的共同特点是（）。

A.圆形

B.多角形

C.椭圆形

D.V字型