Please remind me in case I ______ forget.

 ---The book _____ be Tom’s.---No, it _____ be his. There’s a name on the book. It’s Jim’s.

They _____ have arrived at lunch time but the flight was delayed.

It             be the vocabulary that caused you the problem in the exercise because you know a lot of words.

If people eat natural poisons by mistake, they ________ go to hospital without delay.