ZYJ7电液转辙机开闭器拉簧拉力过大或过小都不能保证接点顺利转换。（）
参考答案：错
About half of million of Afghans have no_______ to basic health services due to continued war and
conflicts.[ ]
A. means
B. approach
C. channel
D. access
下列计算正确的是（ ）
A．a2+a3=a5
B．a6÷a3=a2
C．4x2-3x2=1
D．（-2x2y）3=-8x6y3
