Tại một buổi lễ có 13 cặp vợ chồng tham dự, mỗi ông bắt tay với mọi người trừ vợ mình. Các bà không ai bắt tay với nhau. Hỏi có bao nhiêu các bắt tay ?

A. 78

B. 185 

C. 234

D. 312

Trong các khẳng định sau, khẳng định nào đúng?

A. BCNN của a và b là số nhỏ nhất trong tập hợp bội chung của a và b

B. BCNN(a, b, 1) = BCNN(a, b)

C. Nếu m ⋮ n thì BCNN (m; n) = n

D. Nếu UCLN(x, y) = 1 thì BCNN(x, y) = 1

Rewrite the following sentences without changing the meaning

Because Jane’s father is weak, he can’t push the car.

Jane’s father isn’t ___________

Read the passage and choose the best answer

Alexander Graham Bell was born in 1847 in Edinburgh, Scotland. His father was an expert in phonetics, the study of the sounds of languages. As a boy, Bell became interested in sounds and speech. In 1870 the Bells decided to emigrate to America. They lived in Boston, where Alexander taught in a school for the deaf – mutes. There, he began experimenting with a machine to help the deaf hear. While experimenting with this machine, Bell had an idea. Why not use electricity to send the human voice from one place to another? Bell began work on a new invention of the telephone.

What does the word “emigrate” in line 3 mean?

A. leaves somebody’s country to live in another country.

B. goes to a place for a short time.

C. travels a long way from home to work every day.

D. gets away from something dangerous.