照明电路开关应装在（）。
A.相线上；
B.地线上；
C.相线和地线都行；
D.中性线上。
参考答案：A
与一块骨骼肌相连的骨至少有 [ ]
A．1块
B．2块
C．3块
D．4块
Many scientists say that it's important for us to have ______ food in our diet. [ ]
A. a variety of
B. a great deal
C. a large number of
D. a good many
