What have you learned from your experience in Thailand?—Well, meeting people from another culture ______ be very difficult．

下列各句中，没有语病的一句是（ ）

How amazing it is that astronauts are exploring outer space! -It’s a challenge, I guess, _________man against nature

— Is there any better way to help my son get rid of the habit of playing computer games?— To tell you the truth, it’s very hard. But we on this problem to improve the situation.[ ]

下列各句中没有语病，句意明确的一项是