Sometimes smiles ______ be false, hiding other feelings like anger, fear or worry.

He ________ sleep, although he tried to, when he got on such a hunt for an idea until he had caught it.

—Whose schoolbag is this?—It ___________ be Mary’s. It has her name on it.

—Has Mr.Tom White arrived ? ---- Yes ,already .  ______he wait outside or just come in ?

You _____ read a book in the sun—it'll do harm to your eyes．