Có các chất sau: CuO; MgO; ZnCl2 ; Fe2O3; Na2O; O2; PbO; H2O.

Số chất phản ứng được với H2 ở nhiệt độ cao là:

A. 1

B. 2

C. 3

D. 4

Đốt cháy 3,1 gam photpho trong bình chứa 4,8 gam oxi. Sau phản ứng chất nào còn dư?

A. cả hai đều phản ứng hết.

B. photpho.

C. không xác định được.

D. khí oxi.

A hurricane is a huge storm that forms over warm ocean water. Bands of thunderstorms form and swirl around and around because the rotation of the earth. As more and more thunderstorms form, the hurricane gets bigger and bigger. A hurricane is one of the world's worst storms because it can last for days or weeks.

Hurricanes can also be very large. They may cover hundreds of miles and affect large areas of land. For a storm to be classified as a hurricane, wind speeds within the storm have to reach at least 74 per hour. But hurricane winds can reach speeds of over 155 miles per hour! A large amount of destruction may occur with winds that strong. Roofs may be torn off homes. Buildings may be flattened. Trees topple over. Hurricanes are deadly, but not just because of their winds. They can also produce very heavy rains and huge waves that slam into the coastline. Hurricanes are very common along the east coast of the United States. Here, wind, waves, and rain do the most damage.

Luckily, meteorologists (people who study weather) can forecast hurricanes days in advance by using radar technology. Radar is a little bit like a moving picture. It shows how big storms are and which way they are moving. Radar images people time to prepare for a coming storm. If the storm is very strong, home and business owners will put up plywood to protect their glass windows and doors. People who live along the coast will evacuate. They'll go to a hurricane shelter or stay with friends and relatives who live in safer places farther inland. Many lives are saved every year by people who take the necessary precautions.

Question28. What is a hurricane?

A. a tidal wave B. a huge storm C. a thunderstorm D. a tsunami

Question 29. What makes a hurricane?

A. thunderstorms B. strong winds C. seawater D. the earth rotation

Question 30. What of the following is not correct?

A. A hurricane is very dangerous because it lasts for days and weeks.

B. The hurricane wind speeds per hour can be nearly twice as fast as the wind speeds.

C. A hurricane can reach speeds of at least 74 km per hour.

D. Hurricanes often appear along the east coast of the United States.

Question 31. Who is meteorologist?

A. People study weather.

B. People do businesses in the meteorological field.

C. People live along the coast.

D. People are evacuated from the regions affected by hurricanes.

Question 32. What is radar used for?

A. making moving pictures

B. showing the size of hurricanes and their movements

C. giving people time to prepare for a coming storm

D. All above

The leaves of these trees are ________to cattle

A. poisoner

B. poison

C. poisoning

D. poisonous

Bài 4: Chứng tỏ các bất đẳng thức sau luôn đúng:

a)(m-2\(^{ }\))\(^2\) > m(m-4)

b)2mn ≤ m\(^2\) + n\(^2\)

c)m\(^2\) -m ≤ 50m\(^2\) -15m+1

d)\(\frac{m}{m^2+1}\)≤\(\frac{1}{2}\)

e)\(\frac{ab}{c}\)+\(\frac{bc}{a}\)+\(\frac{ca}{b}\)≥a+b+c (a>0; b>0; c>0)