After he ... all the letters, he took them to the post office.

A. had written          B. has written          C. was writing          D. wrote

Helen is talking to Jane.

- Helen: "Congratulations! You've done very well."

- Jane: "..."

A. That's alright          B. Thank you          C. Good job          D. It's my pleasure

John lost the ... that his parents bought for him last week.

A. beautiful bicycle blue          B. beautiful blue bicycle          C. bicycle beautiful blue          D. blue beautiful bicycle

Michale felt tired. ..., he went to work and tried to concentrate.

A. However          B. Therefore          C. So          D. But

People who do skilled work, making things with their hands are called ... .

A. visitors          B. producers          C. artisans          D. workers

... are trying to develop a vaccine against the disease.

A. Science          B. Scientific          C. Scientists          D. Scientifically

This is a difficult problem. I wish i ... the answer.

A. knew          B. knowing          C. know          D. known

Peter ... have lunch in the school canteen when he was in grade 6.

A. was used to          B. is used to          C. used to          D. gets used to

Traffic ... in Vietnam usually occur in such big cities as Hanoi and Ho Chi Minh City.

A. jams          B. system          C. safety          D. light

You will become ill ... you stop working so hard.

A. until           B. unless          C. if          D. when

City dwellers are more likely to ... stress and anxiety than people who live in the countryside.

A. put up with          B. get over          C. suffer from          D. look forward to

The first Earth Day was held ... April 22, 1970.

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

Mr.Tan, ... teaches physics here, speaks very well English.

A. whom          B. which          C. who          D. that

Ann couldn't go to my birthday party last night because she had to ... her younger sister.

A. look after          B. look up          C. look at          D. look for

Tuan is a good student. He always answers the teacher's questions very ... .

A. quickly          B. more quick          C. good          D. rapid

... are trying to develop a vaccine against the disease.

A. Science          B. Scientific          C. Scientists          D. Scientifically

Cho pt \(x^2-\left(2m+5\right)x+2m+1=0\). Tìm m để pt có 2 nghiệm \(x_1\), \(x_2\) thỏa mãn \(P=\left|\sqrt{x_1}-\sqrt{x_2}\right|\) đạt GTNN.

Cho phương trình \(x^2+x-m=0\). Tìm m để phương trình có 2 nghiệm phân biệt \(x_1\), \(x_2\) thỏa mãn \(x_1^3+mx_2=-3\).