题干

下列实验的先后顺序正确的是(   )

A:称量物质的质量时,先加质量大的砝码,后加质量小的砝码

B:向试管中滴加少量液体药品时,先把滴管伸入试管内,后捏橡胶头向试管中滴入液体药品

C:测定溶液的pH时,先用水润湿pH试纸,后蘸取溶液滴在pH试纸上

D:稀释浓硫酸时,先在烧杯倒入浓硫酸,后向烧杯中缓慢注入水

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答案(点此获取答案解析)

A

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    Powell was walking home one dark night. As he1the city bridge, he noticed something 2--a person was sitting on the rail, legs hanging over a3 about 100 feet below, at this time.

    “At first I thought he was just4 But as I got closer, I heard him whispering.5I clearly heard ‘I'm just going to jump,'” said Powell.

    “Hey, buddy, what are you doing?” Powell asked. He kept his6, standing about six feet away not to 7the guy.

    “I'm going to jump,” the guy said.

    “His8had pain in it, but I could9he didn't really want to do this. He10felt there wasn't any other way.” said Powell.

    Powell sought to11him. “You have any kids?”

    Without turning to look at Powell, the stranger only showed a12of his daughter on his cell phone. She looked to be two years old. “Think about how13her dad at a young age will affect her.” Powell14 Over the next ten minutes they talked, the stranger gradually opened his heart.

    “I'm having a15time.” the stranger said. “I can't make any money and I'm hungry.”

    Thankfully, Powell's calm, sincere persuasion caused the stranger to16turn and look at him. Powell, now about two feet from the stranger, held out his hand and17it there. “I felt I could catch him18if he jumped, but I also wanted him to know that I was there for him.” he said. To his19 the stranger took his hand and climbed down.

    Powell is great! It's always good to offer help and show your care if you find someone in your life20with disappointment.