Cho sơ đồ chuyển hóa:

X+NaOH−−−−→Yto←(CH3COO)2CaX→+NaOHY←to(CH3COO)2Ca

X, Y đều là những chất hữu cơ đơn chức hơn kém nhau 1 nguyên tử C.

Giải phương trình: $\sqrt{2}$cos($\frac{\pi }{4}$-3x) = -1

Đại hội đại biểu toàn quốc lần thứ ba của đảng lao động Việt Nam một tháng chín một chín sáu mươi đã xác định nhiệm vụ chiến lược

Đốt cháy 65kg hỗn hợp gồm $Fe{S}_2$ và ZnS ta thu được 20,16 lít khí $S{O}_2$. Xác định khối lượng của mỗi chất trong hỗn hợp ban đầu

1.(2x+3y)'2

2.(3x-2y)'2

3.(5x-y)'2

4.(x+1/4)'2

5( x/2+2y'2).(x/2-2y'2)

Cho em xin nhận định hoặc các ý kiến liên quan đến bài thơ "Nhàn" của Nguyễn Bỉnh Khiêm (L10) ạ

I don't know what they are going to ask in the job interview. I'll just play it by ear.

Most universities have trained counselors who can reassure and console students who have academic or personal problems.

A. satisfy B. sympathize C. please  D. discourage

Though I persuaded my boss to solve a very serious problem in the new management system, he just made light of it.

In a study, more Asian students than American students hold a belief that a husband is obliged to tell

A. urged B. free C. required  D. sugges

Yes, I suppose she was but she'd changed so much. She used to be chubby, but now she was all skin and bone

She came in and turned up the TV. Her favourite programme had just begun.

Due to the efforts of conservationists and environmentalists, few people are unaware the problems of endangered species.

 A. ignorant of B. well-informed of C. indifferent to D. adjustment to 

 Contrary to popular belief this kind of snake is quite innocuous.

 In the past, energy source was thought to be boundless.

I wonder if I would answer the following personal questions.

A. individual

B. private 2

C. public

D. owned 

I wonder if I would answer the following personal questions.

A. individual B. private C. public D. owned

The thief hid his breclouenossessions in the well behind his house.

A. inexpensive B. robbed  C. valuable  D. worthless 

 He was respected by all of the colleagues who used to work with him for years

D. looked up to

A. looked down on

C. complied with B. ignored

bài tập trái nghia

Adverse weather conditions made it difficult to play the game.

D. severe A. favorable  C. comfortable   B. bad 

During the five-decade history the Asian Games have been advancing in all aspects. OPPOSITE

 A. holding back

 B. holding at

 C. holding by

 D. holding to

Fruit and vegetables grew in abundance on the island. The islanders even exported the surplus. OPPOSITE

 A. large quantity

 B. excess

 C. small quantity

 D. sufficiency

My friend Albert as decided to buy a motorbike. His car was stolen last week. 

 A. My friend Albert, whose car was stolen last week, has decided to buy a motorbike.

 B. My friend Albert whose car was stolen last week has decided to buy a motorbike.

 C. My friend Albert has decided to buy a motorbike which car stolen last week.

 D. My friend Albert has decided to buy a motorbike has his car stolen last week.

After finishing the duty at the company at 6 p.m.

- Anna: “Shall we eat out tonight?”

- Jane: “___________”

 A. It is very kind of you to invite me.               B. You are very welcome.

C. That‟s a great idea.            D. That‟s understandable

Jack is going to London to study next week.

- Betty: “____________”

- Jack: “Thanks. I will write to you when I come to London.” 

 A. Better luck next time!                                   B. Have a go!

_____ long _____ his brother was at the party last night. They were both busy.

 A. Neither/ nor            B. Both/ and                   C. Either/ or                   D. Neither/ or

Not only _____ the exam but she also got a scholarship.

 A. has she passed        B. she has passed           C. she passed                 D. did she passed

Benald wanted to know _____.

 A. where I have been those days.                      B. where I had been those day.

 C. where had I been those days.                        D. where I had been those days.

The clown was wearing a _____ wig and red nose.

            A. red funny plastic    B. red plastic funny    C. funny red nose        D. funny plastic red

¼ of my income _____ to pay for my university debts.

   A. has been used         B. were used                  C. has used                     D. are used

¼ of my income _____ to pay for my university debts.

   A. has been used         B. were used                  C. has used                     D. are used

Due to severe weather condition, we had to wait long hours _____ the airport.

   A. in                            B. at                               C. from                           D. on

I have asked my boss _____ me one day- off to see the doctor.

   A. to give                    B. that he give                C. giving                        D. if could he give

Despite many recent _____ advances, there are parts where schools are not equipped with computers

Many African and Asian nations have set aside land called _____ to protects the habitats of elephants and other wild animals.

   A. reserves                  B. wildlife                      C. species                       D. forest