一定用英文翻译

What？你说的是什么？

I must make a living wandering from place to place in the next year我自己翻译的可能不准确

be sure to

The students have acquired a somewhat large vocabulary

I must make a living by wandering from place to place next year.

是Must be

Must be, may be, can't be, can't be in, just must be, just may be, may have is, now must be, just must be

一定是 must be，可能是 may be，might be不可能是 can't be，不可能是在 can be doing sth. ，刚才肯定是must have been doing sth just now，刚才可能是 might be doing sth just now ，以前可能是 may had been，现在一定是 must be sth/ doing sth ，刚才一定是 must have been (话说这和 “刚才肯定是”是一个意思吧...)