15. 

-> The teacher told her students to do the test carefully. ( 'do' -> adv )

16.

-> I think it is really good to spend time on pronunciation English. ( spend ... on Ving : dành thời gian làm gì đó )

17. 

-> My father told me not to touch his paper on that table. ( told ... ( not ) to ... : bảo ai ( k ) làm điều gì đó )

18.

-> She speaks English very well. ( 'speak' -> adv )

19.

-> John used to go on barefoot when he was a little boy. ( used to Vo : đã từng )

20. 

-> I learn English so as to communicate with foreigners. ( so as to = to : để mà )