Đốt cháy hoàn toàn 20 ml hơi hợp chất hữu cơ X (chỉ gồm C, H, O) cần vừa đủ 110 ml khí O₂, thu được 160 ml hỗn hợp Y gồm khí và hơi. Dẫn Y qua dung dịch H₂SO₄ đặc (dư), còn lại 80 ml khí Z. Biết các thể tích khí và hơi đo ở cùng điều kiện. Công thức phân tử của X là:

A. C₄H₁₀O

B. C₄H₈O

C. C₃H₈O

D. C₄H₈O₂

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each pair of sentences in the following questions.

It is difficult to get tickets for 2018 World Cup. It was wise of him to buy the tickets for 2018 World Cup in advance.

A. Since they are difficult to get, he should have brought the tickets for 2018 World Cup beforehand

B. Although he bought the tickets for 2018 World Cup in advance, he wasn’t wise enough to do so

C. Such is te difficulty in getting the tickets for 2018 World Cup that it was wise of him to buy them beforehand

D. The tickets for 2018 World Cup is so difficult to get that he had enough wisdom to buy them