30) Poison is harmful (to/with/for/about) humans.
31) Cheques are useful (with/to/for/on) travellers.
32) Are you successful (on/in/at/to) your experiment?
33) She got back safe (for/from/with/to) her adventure.
34) It was very lucky (to/for/of/with) me that my bag was found.
35) He seems friendly (on/to/for/about) everyone in the village.
36) She was sad (about/for/with/to) my refusal.
37) Quang Linh is popular (with/for/to/in) folk songs.
38) The student is quick (with/at/on/to) understanding what the teacher explains.
39) The story is very pleasant (to/with/for/in) us.
40) He is very kind (to/of/with/for) me.