xl mk thi vấn đáp bn ak....

1-d dương

2-b

HĐT 20V bn ak!

Lớp cá : Cá chép, cá trắm...

Lớp lưỡng cư : Ếch đồng , cóc , ngóe..

Lớp bó sát : Thằn lằn , cá sấu ,....

Lớp chim : Chim bồ câu , ...

Lớp thú: Thỏ , chuột chù,......

Chúc bn hok tốt nha....>.<

Mắc song song.

Chúng sẽ đẩy nhau.

Điều kiện n \(\in\) N

17n; 17n+1; 17n+2 là 3 số nguyên liên tiếp nên có đúng một số chia hết cho 3 
Nếu n chia hết cho 3 => 17n chia hết cho 3 => (17n+1) và (17n+2) đều không chia hết cho 3, mà 3 là số nguyên tố => (17n+1)(17n+2) không chia hết cho 3 

Thấy 17 và 3 là hai số nguyên tố cùng nhau nên nếu n không chi hết cho 3 thì 17n cũng không chia hết cho 3 => (17n+1) hoặc (17n+2) có một số chia hết cho 3 
=> (17n+1)(17n+2) chia hết cho 3 

Tóm lại (17n+1)(17n+2) chia hết cho 3 

In developing centuries, many household depend ______ the use of the natural resources to ensure the food supply or the income required to purchase food.

A. with

B. on

C. in

D. at

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

Ever since it was first possible to make a real robot, people have been hoping for the invention of a machine that would do all the necessary jobs around the house. If boring and repetitive factory work could be (37) ________ by robots, why not boring and repetitive household chores too? 
For a long time the only people who really gave the problem their attention were amateur inventors And they came up against a major difficulty. That is, housework is actually very complex It has never been one job it has always been many. A factor robot (38) ________ one task endlessly until it is reprogrammed to do something else. It doesn’t run the whole factory. A housework robot on the other hand, has to do several different (39) ________ of cleaning and carrying jobs and also has to cope (40) ________ all the different shapes and positions of rooms, furniture, ornaments, cats and dogs. (41) ________, there have been some developments recently. Sensors are available to help the robot locate objects and avoid obstacles. We have the technology to produce the hardware. All that is missing the software- the programs that will operate the machine.
Question 41:

A. However

B. Therefore

C. Besides

D. Moreover

có bn'