=>
16. It is said that she has a beautiful voice.
-> chủ động : people/they say that S V -> bị động : It is said that S V
17. They used to go to school on foot in the past.
-> used to V : đã từng
18. I buy some snack so that we can have something to eat on the way to the beach.
-> so that S V (chỉ mục đích : để)
19. Let's go to the cinema early so that we can get good seats.
-> so that S V
20. He decided to stay at home so as to watch the football match on TV.
-> so as to V : để làm gì