搜题请搜索小程序“爱下问搜题”
问题 单项选择题

当用一块数字万用表测量市电的电压时，每隔2分钟测试一次，重复测量10次，数值相差造成的误差称为（）。

A、随机误差

B、系统误差

C、疏忽误差

D、相对误差

答案

参考答案：A

完形填空

缺词填空 （6分）

The room goes dark. The audience becomes quiet. The music begins. The movie starts. In the US, it is

g   1   to see parents watching cartoons with their children, or a group of male friends watching an action film together.

People often eat popcorn in the c   2  . They drink soda. Theaters also sell candy and chocolate. S  3   people bring their own food in to save m   4   .

But how do you know which films you can w   5  ? The US has a rating(分级) system. If a movie is rated G, it means General Audience, and a   6   can see it. PG means Parental Guidance(家长指导). That means you need your p   7   to go with you, if you’re really young. A PG-13 movie means you h   8   to watch it with your parents if you’re y   9   than 13 years old. And a   10    R rated movie means unless you’re o   11   than 17, you need your parents to be w   12   you.
查看答案
选择题

.John sold the camera yesterday which his brother ________ him as a birthday present from Japan.

A．has sent

B．had sent

C．was sending

D．would send
查看答案