We use one (singular) and ones (plural) to avoid unnecessary repetition. *See those two girls? Helen is the tall one and Jane is the short one. *Which is your car, the red one or the blue one? *My trousers are torn. I need some new ones. *See those two girls. Helen is the one on the left. *Let’s look at the photographs. The ones you took in Paris. We often use them after Which ... in questions: *You can borrow a book. Which one do you want? *There are lots of books here. Which ones are yours?

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