题目

If you're out for a run, what difference does it make if you're able to tough it out for another 50 seconds? If you're less than a minute from the top of the hill, that extra time can make the difference between having reached your goal and snatching defeat from the jaws of victory.How do you get those extra seconds of energy? A research team at the Texes Tech University developed a study to measure what effect listening to music would have on exercise tolerance. The researchers based the study on a stress testing. As part of the testing, they noted any changes in heart rate and blood pressure下列基本操作正确的是 [　　] A．手持试管给试管里的物质加热 B．用燃着的酒精灯去点燃另一只酒精灯 C．用天平称量药品时用手直接拿砝码 D．用滴管滴加液体时滴管应垂悬在容器上方不能触及容器内壁