动词短语 to clam up 用来形容一个人因为紧张，尴尬或不想谈论某件事而沉默不语。

例句

Adam was very naughty and ate all the cookies. When his mother asked where they were he clammed up and couldn't tell her.

When I was young I used to clam up when a stranger asked me a question.

请注意

另一个短语 the world is your oyster 意思是世界属于你，机遇很多，万事顺心，可随心所欲。

Now that you have your college degree, the world is your oyster!