实验基本操作是学习化学的灵魂.以下实验操作中正确的是( )
A.
倾倒液体
B.
浓硫酸的稀释
C.
干燥氧气
D.
测定某溶液的pH
答案:A
将下列表示单数的句子改成复数的句子。
1. This is a box.
_____________________________________________________
2. Do you have a new radio?
3. There is one peach in my hand.
4. She has a camera and an umbrella.
5. He is a driver.
6. That is her watch.
7. He is a policeman.
8. He has a good friend.
9. What is that?
10. This is a tomato.
两样本均数差别的显著性检验用t检验的条件是()
A.两总体符合正态分布
B.两总体均数相等
C.两总体方差(标准差的平方)相等
D.两样本例数很大
E.两样本分组一致