主要含神经毒的毒蛇是( )
A．竹叶青蛇B．尖吻蝮蛇C．眼镜王蛇D．烙铁头蛇E．银环蛇
参考答案：E
—Susan, go and join your sister cleaning the yard.
—Why ? John is sitting there doing nothing. [ ]
A. him
B. he
C. I
D. me
脱吸因数S在Y-X图上的几何意义是（）。
