Hợp chất thơm X có công thức phân tử C₇H₈O₂. Khi cho a mol X tác dụng với Na dư thì thu được 22,4a lít H₂ (đktc). Mặt khác a mol X tác dụng vừa đủ với a lít dung dịch KOH 1M. Số chất X thỏa mãn là

A. 4

B. 3

C. 2

D. 1

Số đồng phân ancol là hợp chất bền ứng với công thức C₃H₈O_x là

A. 5

B. 3

C. 4

D. 6

Từ bảng 17.2 (SGK), hãy so sánh và nhận xét sự thay đổi cơ cấu lao động theo nhóm ngành kinh tế ở nước ta giai đoạn 2000 - 2005.

Read the following passage and mark the letter A, B, C or B on your answer sheet to indicate the correct answer to each of the questions from 30 to 37.

  Because writing has become so important in our culture, we sometimes think of it as more real than speech. A little thought, however, will show why speech is primary and writing secondary to language. Human beings have been writing at least 5,000 years, but they have been talking for much longer, doubtless ever since there have been human beings. When writing developed, it was derived from and represented speech, although imperfectly. Even today, there are spoken languages that have no written form. Furthermore, we all learn to talk well before we learn to write; any child who is not severely handicapped physically or mentally will learn to talk: a normal man cannot be prevented from doing so. On the other hand, it takes a special effort to learn to write; in the past, many intelligent and useful members of society did not acquire the skill, and even today many who speak languages with writing systems never learn to read or write while some who learn the rudiments of those skills do so imperfectly.

  To affirm the primacy of speech over writing is not to disparage the later. One advantage writing has over speech is that it is more permanent and makes possible the records that any civilization must have. Thus, if speaking makes us human, writing makes us civilized.

According to paragraph 1, the author of the passage argues that          

A. writing has become too important in today's society. 

B. speech is more basic to language than writing.

C. everyone who learns to speak must learn to writing. 

D. all languages should have a written form.