21. D ( Need+ V-ing= need+ to be+ PP: Cần đc lm j)
22. C ( Avoid doing sth)
23. C ( prefer V-ing to V-ing)
24. D ( make+ sb+ V-inf)
25. B ( Be made to V: Bị bắt lm j)
26. B (consider+ V-ing)
27. C ( be considered to be: đc coi là)
28. B ( let+ sb+ V-inf/ When+ V-ing)
29. A ( be allowed+ to talk)
30. C ( allow+ V-ing)