搜题请搜索小程序“爱下问搜题”
问题 单项选择题 B1型题

10岁儿童有意注意时间为（）

A.10分钟

B.15分钟

C.20分钟

D.25分钟

E.30分钟

答案

参考答案：D

选择题
He feels relaxed and even begins to whistle because ____ of the distance ____ covered.

A. three fifth; were
B. three fifth; was
C. three fifths; have been
D. three fifths; has been
查看答案
单项选择题

RC串联电路的功率因数COS=0.8QL=3Kvar则视在功率S=（）

A、3KVA

B、4KVA

C、5KVA

D、2KVA
查看答案