经纬仪粗整平时，通过（）或踩踏架腿入土的方法使圆水准器气泡居中。
A.调整脚螺旋
B.伸长或缩短三脚架腿
C.调整微动螺旋
D.重新安置
参考答案：B
阅读短文，判断正(T)误(F)。
My name is Perry. I am ten years old. I have a big family, my grandparents, my father, my mother and I.
My grandparents are old but healthy. Their favourite food is vegetables. My father is strong. He likes pork and
bread. My mother is pretty. She likes hamburgers and juice. We all don't eat many candies (糖果). Because
they're not good for teeth.
( ) 1. There are four people in Perry's family.
( ) 2. Perry's grandparents like vegetables.
( ) 3. Perry's father likes pork and bread.
( ) 4. Perry's mother is pretty.
( ) 5. We all don't eat many candies. Because we don't like candies.
A、B两个电阻阻值分别是10Ω和30Ω．将它们串联后接入电路，总电阻是______Ω，它们两端的电压之比UA：UB是______．若将它们并联后接入电路，则A、B两个电阻中通过的电流之比IA：IB是______．
