giúp ----- Nội dung dịch tự động từ ảnh ----- 46 "Could you turn off the stove? The potatoes --- for at least thirty minutes." A. are boiling C. have been boiling B. were boiling D. boiled 47 Carbon dioxide - as one of the main contributors to the greenhouse effect. A. has been identified C. had identified B. has identified D. had been identified 48 The headmaster has decided that three lecture halls ----------- in our school next semester. A. will build C. are being built B. will be build D. will be building 49 Although MERS spreads through close contact with sick people, not through the air, many people still avoid -- to crowded places. A. to go C. gone B. having gone D. going 50 Students will not be allowed into the exam room if they ---- their student cards. A. produced C. didn't produce B. hadn't produced D. don't produce