D Fill in the correct preposition

• 16 If a burglar breaks into your house, always hand over your valuables.
• 17 I ran into an old friend at the supermarket yesterday.
• 18 We ran out of milk, so can you buy some when you're at the supermarket?
• 19 My brother and his friends hang out at the shopping centre on Saturdays.
• 20 I saw two policemen running after a burglar.