`39. C`

`-` Dẫn chứng:

`+` Cả bài đang nói về hiện tượng lốc xoáy ('tornadoes')

`+` Most tornadoes form during thunderstorms.

`40. B`

`-` Dẫn chứng: Instead, they are among the most violent and destructive forces in nature.

`41. D`

`-` utterly (adv): hoàn toàn `=` totally (adv): hoàn toàn

`42. B`

`-` Dẫn chứng: A region of the country in the Midwest and Southeast gets many tornadoes. In fact, so many tornadoes happen there that it is called Tornado Alley.

`43. C`

`-` Dẫn chứng:

`+` Most tornadoes form during thunderstorms. `->` `A` đúng

`+` Most tornadoes are fairly thin columnsof air. `->` `B` đúng

`+` Every spring, residents of the states in TornadoAlley always watch the sky when there are storm clouds in it. `->` `D` đúng

`=>` `C` sai, vì: 'Some of the most powerful ones have windsthat move more than 500 kilometers per hour', không phải 'always' (luôn luôn)

39. C

=> D/C: In The Wizard of oz, Dorothy and her dog Toto hide in a farmhouse to avoid a tornado.... Every spring, residents of the states in Tornado Alley always watch the sky when there are storm clouds in it.

40. B

=> D/C: Instead, they are among the most violent and destructive forces in nature.

41. D

- utterly (adv) = totally (adv): hoàn toàn

42. B

=> D/C: A region of the country in the Midwest and Southeast gets many tornadoes. In fact, so many tornadoes happen there that it is called Tornado Alley.

43. C

=> D/C:

A. Most tornadoes form during thunderstorms. 

B. Most tornadoes are fairly thin columnsof air. 

C. Some of the most powerful ones have windsthat move more than 500 kilometers per hour.

D. Every spring, residents of the states in TornadoAlley always watch the sky when there are storm clouds in it.