Can I carry this bag on?/Can I take this on board? /Can I hand-carry this? 我可以带这个登机吗？

Ground staff: Yes, that would be fine. 可以，没问题。/ No. You need to check it in. 不行，你必须托运。

carry-on 随身行李

on board 登机

check （在机场指托运）托运+in, 酒店指寄存行李

对话：

L: How many bags would you like to check in? 你有几个包包要托运呢？

D: Um, I've got one bag, but can I carry this on board? 我有一个包包，但是我可以带这个登机吗？

L: Yeah, that would be fine! 可以，没问题！