Ứng với công thức phân tử C₃H₆O có bao nhiêu hợp chất mạch hở bền khi tác dụng với khí H₂ (xúc tác Ni, t^o) sinh ra ancol

A. 4.

B. 2

C. 3

D. 1

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

THE HISTORY OF WRITING

The development of writing (30) _______ a huge difference to the world and might see it as the beginning of the media. Pieces of pottery with marks on that are probably numbers have been discovered in China (31) _______ date from around 4000 BC. Hieroglyphics and other forms of "picture writing" developed in the area around Mesopotamia (modern-day Iraq), where the ancient Sumerian civilization was based, from around 3300 BC onwards. However, the first (32) _______ alphabet was used by the Phoenicians around 1050 BC. Their alphabet had 22 letters and it is estimated that it lasted for 1000 years. The first two signs were called "aleph" and "beth", which in Greek became "alpha" and "beta", which gave us the modern word "alphabet".

The modern European alphabet is based on the Greek and spread (33) _______ other European countries under the Romans. A number of changes took place as time passed. The Romans added the letter G, and the letter J and V were unknown to people in Shakespeare's time.

If we (34) _______ the history of punctuation, we also find some interesting facts. The Romans used to write quaesto at the end of a sentence in order to show that it was a Question. They started to write Qo in place of the whole word, and then put the Q above the o. In the end, that became the question mark "?"

Điền vào ô trống 33

A. to

B. in

C. with

D. for

Hoà tan 14,2 gam hỗn hợp X gồm MgCO₃ và một muối cacbonat của kim loại M vào một lượng vừa đủ axit HCl 7,3%, thu được dung dịch Y và 3,36 lít khí CO₂ (đktc). Nồng độ MgCl₂ trong Y là 6,028%. Cho dung dịch NaOH dư vào dung dịch Y, lọc lấy kết tủa đem nung ngoài không khí đến khối lượng không đổi thì thu được m gam chấy rắn. Giá trị của m là

A. 7,6.

B. 10,4.

C. 8,0.

D. 12,0.

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

The doctors hope to _____________ the source of the infection which has been a mystery for the medical community since its discovery.

A. trend down

B. back down 

C. push down

D. track down