$1. Bob used to smoke a lot but now she doesn't smoke any more.
`->`used to + V-inf: đã từng làm gì trong QK.
$2. Wearing uniforms encourages students to be proud of their school.
`->`encourage + O + to V: khuyến khích, động viên ai đó làm gì
$3$. In the end, I decided not to buy that camera because it was too expensive
`->`decide ( not ) + to V: quyết định ( không ) làm gì
$4$. He started learning play the piano when his age was 5.
`->`QKTD + when + QKD
`->`start + V-ing: bắt đầu làm việc gì đó
$5$. Learning a foreign language is necessary for us to get a good job.
`->`necessary + ( for sb ) + to V: ai đó cần làm gì