Hỗn hợp X gồm olefin Y và hiđro có tỉ khối so với He là 3,2. Dẫn X đi qua bột Ni nung nóng cho đến khi phản ứng xảy ra hoàn toàn, thu được hỗn hợp Z có tỉ khối so với H₂ là 8. Vậy công thức phân tử của Y là

A. C₂H₄

B. C₄H₈

C. C₅H₁₀

D. C₃H₆

Giai đoạn mới của cách mạng Việt Nam sau khi kết thúc thắng lợi cuộc kháng chiến chống Mĩ, cứu nước thể hiện như thế nào?

Dẫn từ từ đến dư khí CO₂ vào dung dịch Ba(OH)₂. Sự phụ thuộc của khối lượng kết tủa (y gam) vào thể tích khí CO₂ tham gia phản ứng (x lít) được biểu diễn bằng đồ thị bên. Giá trị của m là 

A. 19,70. 

B. 39,40. 

C. 9,85. 

D. 29,55. 

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following question.

               in business, one must be prepared to take risks.

A. Succeeding

B. Success

C. To succeed

D. Succeed

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 36 to 42.

Jupiter is the largest and most massive planet and is fifth in order of distance from the sun. It is well placed for observation for several months in every year and on average is the brightest of the planets apart from Venus, though for relatively brief periods Mars may outshine it. Jupiter's less than 10 hour rotation period gives it the shortest day in the solar system in so far as the principal planets are concerned. There are no true seasons on Jupiter because the axial inclination to the perpendicular of the orbital plane is only just over 3°-less than that for any other planet.

The most famous mark on Jupiter is the Great Red Spot. It has shown variations in both intensity and color, and at times it has been invisible, but it always returns after a few years. At its greatest extent it may be 40,000 kilometers long and 14,000 kilometers wide, so its surface area is greater than that of Earth. Though the latitude of the Red Spot varies little, it drifts about in longitude. Over the past century the total longitudinal drift has amounted to approximately 1200°. The latitude is generally very close to -22°. It was once thought that the Red Spot might be a solid or semisolid body floating in Jupiter's outer gas. However, the Pioneer and Voyager results have refuted that idea and proven the Red Spot to be a phenomenon of Jovian meteorology. Its longevity may well due to its exceptional size, but there are signs that it is decreasing in size, and it may not be permanent. Several smaller red spots have been seen occasionally but have not lasted.

According to the passage, which of the following is NOT true?

A. Jupiter is bigger than all the other planest in the solar system.

B. A day in Jupiter is nearly 10 hours long.

C. The Red Great Spot moves more vertically than horizontally.

D. Scientists have proof showing that smaller red spots are increasing their size to become other Great Red Spots.