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盏酒精灯
C:用天平称取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
作为小历史学家的你,如果想要研究唐朝时印度和西亚的历史,最好的参考书是( )
若存在实数x∈1,2满足2x2﹣ax+2>0,则实数a的取值范围是____ .
He had wanted to write ____children's book for many years, but one thing or another always got in _________ way.