46.she has studied English since 2017-S+has/have+Ved/c3.....t/g htht
47.it is very important to keep the environment clea-it is+adj/adv+toV
48.unless you take care of thosed shoes,they won't fast for long-unless+S1+V1(vế này luôn kđ)...S2+V2
49.she said that she came from Japan-câu gián tiếp trong câu trần thuật;come->came
50.because Thanh was tired,he went to bed early last night-because+S1+V1...S2+V2