I ________ work out the problem at first, but after my teacher showed me an example, I ________ get the answer easily.

–Look at that girl! Is it Susan? --No, it _______ be her. She went to her hometown just now.

The book ________ be Tom’s. Look! His name is on it.

She ______ have attended that meeting, for she was doing paperwork in the office then.

As it turned out to be the most important meeting in the year, you ____ so casually.