—Did you know China is one of the oldest countries in the world?
—Yes, I did. It’s ______ than the US.
Which do you prefer to use to keep in touch with your friends, QQ_____ WeChat？
如图，空间四边形ABCD的对角线AC，BD相等，顺次连接各边中点E，F，G，H，则四边形EFGH一定是（ ）
