32. A (to ⇒ on) 

go on a vacation: đi nghỉ mát 

33. C (environmentalist ⇒ environmentalists) 

one of + N số nhiều: 1 trong những 

34. Mai said that her sister was a singer and she earned a lot of money.

S + said +(that) + S+ V (lùi thì)

HTĐ ⇒ QKĐ

35. Although that smartphone's memory isn't so large, Mr. Smith wants to buy it.

Although + clause, clause: mặc dù 

`color{orange}{~MiaMB~}`