因为圆柱的体积÷高=πr2，直径一定，半径就一定，则底面积一定，则高和体积成正比例；
故选：A．
测量tgδ常用QS1电桥是按（）刻度的。
A.R4=10000/πΩ tgδ（%）=C4
B.R4=1000/πΩ tgδ（%）=C4
C.R4=100/πΩ tgδ（%）=C4
Everyone is supposed ____ a seat belt in the car.[ ]
A. wearing
B. to wear
C. to be worn
D. wears
