Her mother often forgets the door but this morning she remembered it.
A:to close; to close
B:closing; closing
C:to close; closing
如图,△ABC与△DEF位似,位似中心为点O,且△ABC的面积等于△DEF面积的 49 ,则AB:DE=____
—I'm afraid I can't travel with you.—Don't worry. We'll going on vacation until you're better.
如图所示的现象可以用光的折射解释的是( )