20% của 520 là:

A.  401

B.   104

C. 140 

Hỗn số 8  5 100 bằng số thập phân nào trong các số sau :

A. 8,05

B. 8,5

C. 8,005

Choose the best answer (A, B, C, D) to complete the following sentences.

Vietnam is ________ multi-cultural country with 54 ethnic groups.

A. a

B. the

C. X

D. an

Cho hình chóp S.ABCD có đáy ABCD là hình thoi, O là giao điểm của 2 đường chéo và SA = SC. Các khẳng định sau, khẳng định nào đúng?

A.  S A ⊥ A B C D  

B.  B D ⊥ S A C  

C.  A C ⊥ S B D  

D.  A B ⊥ S A C  

Read the passage, and choose the correct answer A, B, C or D for each question.

Son Doong Cave

Located in the limestone mountains of Phong Nha - Ke Bang National Park. Son Doong Cave was first found in 1991 by Ho Khanh, a local man. In 2009, the cave was explored and published by a group of scientists from British Cave Research Association.

Son Doong Cave was formed from 2 to 5 million years ago, when the river flowed through the limestone mountain area and was buried. The water eroded limestone and created an underground tunnel. In soft limestone areas, the collapse of tunnel ceiling formed large holes which became giant domes afterward. The cave is about 200m high, 200m wide and at least 8 5km long. Especially, Son Doong consists of two entrances, which is unique among explored caves in Phong Nha - Ke Bang National Park. Exploring the cave, visitors were surprised with spectacular scenery of numerous stalactites of which some giant stalagmites are more than 70 metres high. Deep inside the cave exists a grandiose tropical jungle called “Garden of Eden" by the explorers. The jungle is home to a diversifiedsystem of fauna and flora. Besides, the cave possesses a 2.5-kilometre underground river. Not far from the “Garden of Eden” lies an enormous “pearl collection” consisting of tens of thousands of small stone pieces in dry ponds, contributing to magnificent beauty of the cave.

The most important feature of “Garden of Eden” is ………

A.the biodiversity

B. giant stalagmites

C. the biggest length

D. the river below

Các loại gió nào dưới đây biểu hiện cho quy luật địa đới? 

A. Gió mậu dịch, gió mùa, gió tây ôn đới

B. Gió mùa, gió tây ôn đới, gió fơn

C. Gió mậu dịch, gió đông cực, gió fơn

D. Gió mậu dịch, gió tây ôn đới, gió đông cực