题干

下列有关实验操作叙述正确的是(   )

A:排水法收集氧气,观察到水中冒气泡就可收集

B:称量氢氧化钠固体时,在天平两边各放一张质量相同的纸

C:稀释浓硫酸时,将浓硫酸慢慢注入量筒中

D:蒸发食盐溶液制晶体,待蒸发皿中出现较多量固体时停止加热

上一题 下一题 0.0难度 选择题 更新时间:2019-12-04 04:18:11

答案(点此获取答案解析)

D

同类题5

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

Weather influences health, intelligence and feelings. ____

In August, it is very hot and wet in the southern part of the United States. ____ In the Northeast and the Middle West, it is very hot at some times and very cold at other times. People in these states have more heart trouble after the weather changes in February or March.

____ For example, in a recent report by scientists, IQ of a group of students was high when a very strong wind came, but after the strong wind, their IQ was 10% lower. The wind can help people have more intelligence. Very hot weather, on the other hand, can make it lower. Students in many schools of the United States often get worse on exams in the hot months of the year.

Weather also has a strong influence on people’s feelings. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel unhappy during cold weather. ____ Generally speaking, at about 18℃, people become stronger and better.

Low air temperature may make people forgetful. People leave more bags on buses and in shops in cold days.

____ sometimes, it may be the weather’s problem.

A, The weather can also influence intelligence.

B, So, different weather makes people feel different.

C, But fat people may have a hard time in hot summer.

D, Are you feeling sad, tired, forgetful, or unhappy today?

E,Warm weather can have a bad effect on health.

F, People there have heart trouble and other kinds of health problems during this month.

G,people may have more intelligence when low air pressure comes.