“刮刮乐” * * 的最大特点是（）。
参考答案：即开即兑
3个连续的自然数的和一定是3的倍数。[ ]
—What's the matter with the man hanging his head there?
—Well，if you ________ know, he was caught stealing my bike.
A．must
B．may
C．can
D．shall
