A:22条+XX
B:22条+XY
C:22条+X或22条+Y
D:22条+X和22条+Y
As is known to us all, taking exercise is b____ to our health.
海豚每小时可以游70千米,比蓝鲸的速度快40%,蓝鲸的速度是每小时多少千米?
苏伊士运河是哪两个大洲的分界线( )