用before, after, when, while, since, until, as soon as或whenever填空。
如图是光线通过凹透镜后的折射光线,作出入射光线.
________ toothache, the old man felt very bitter, having no good sleep.
已知集合A={x|x2﹣2x﹣3≥0},B={x|﹣2≤x<2},则A∩B=( )