Hòa tan m gam hỗn hợp X gồm hai muối vào nước thu được dung dịch chứa 0,05 mol Na + ; 0,1 mol Mg 2 + ; 0,2 mol Cl -  và x mol SO 4 2 - . Giá trị của m là

A. 29,85.

B. 23,7.

C. 16,6

D. 13,05

Số đường chéo xuất phát từ 1 đỉnh của đa giác 20 cạnh là?

A. 15     

B. 16 

C. 17     

D. 18 

Read the following passage carefully, and then select the best option A, B, C or D to complete it

Technology, general term for the processes by (1) _______ human beings fashion tools and machines to increase (2) _______ control and understanding of the material (3) _______. The term is derived from the Greek words tekhnē, which refers to an art or craft, and logia, (4) _______ an area of study; thus, technology means, literally, the study, or science, of crafting.

Many historians of science argue not only that technology is an essential condition of advanced, industrial civilization (5) _______ also that the rate of technological change has developed its (6) _______ momentum in recent centuries. Innovations now (7) _______ to appear at a rate that increases geometrically, (8) _______ respect to geographical limits or political systems. These innovations tend to transform traditional cultural (9) _______, frequently with unexpected social consequences. Thus technology can be conceived as both a creative and a destructive (10) _______.

Question 7:

A. like

B. want

C. love

D. seem