When you need to ask 'which one?' or 'which ones?' from a specific set of options you can see or have just talked about, you can use a special pronoun in French. This pronoun changes depending on the gender and number of the noun it's replacing.

To ask 'which one?' for a masculine singular noun, you use 'lequel'. For example, if you're looking at two coats, and 'manteau' is masculine, you could ask: 'Lequel est-ce que tu préfères ?', meaning 'Which one do you prefer?'.

For a feminine singular noun, the question 'which one?' becomes 'laquelle'. Imagine choosing between two cars. 'Voiture' is feminine, so you would ask: 'Laquelle est la plus rapide ?', meaning 'Which one is the fastest?'.

When you're choosing from multiple masculine items, 'which ones?' is 'lesquels'. For example, talking about some books, where 'livres' is masculine plural, you could ask: 'Lesquels sont les plus intéressants ?', meaning 'Which ones are the most interesting?'.