Gunpowder, in some ways the most effective of all the explosive materials, were a mixture of potassium nitrate, charcoal, and sulfur.

The ozone layer must be protected because it shields the Earth from excessive ultraviolet radiations

Since it was so difficult for American Indians to negotiate a peace treaty or declare war in their native language, they used a universal understood form of sign language.

The purpose of traveler’s checks is to protect travelers from theft and accidental lost of money.

Mark the letter A, B, C, or D to indicate the correct answer to each of the following questions.

On most trains, there is a_________, where you can eat a snack or something hot.

Mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions.
I really believe that you should let your son _____ his own decisions; he is certainly old enough ____ so.

The accounting supervisor was unpleased to learn that the budget report would not be finished by time.

After driving for twenty miles, he suddenly realized that he has been driving in the wrong direction.

Choose the best answer to the following sentences.

More tourists ________ to this country unless it _________ a better climate.

Marta being chosen as the most outstanding student of her campus made her parents very happy.

When I came back, I realized that my camera had been disappeared.

Choose the best answer:
The Pikes put ______ their trip because of bad weather.:

Lawrence Robert Klein received the 1980 Nobel Prize in economics for pioneering the useful of computers to forecast economic activity

VOCABULARY AND STRUCTURES: Choose the best options 

The film is ______ two Women who drive across America. 

If either of you take a vacation now, we won’t be able to finish this work.

Psychologists at the University of Kansas has studied the effects of the color of a room on people’s behaviors.

A teacher at the school acknowledged that, despite government sponsored endeavors to improve classroom performance, an extraordinary high percentage of their students fail to gain admission to higher education.

Choose the best answer:

A: ________________________________

B: Vatican City has the smallest population in the world ... only eight hundred people live there!

If  a glass lizard loses its tails, a new one grows to replace it.

Tests have been performed to determine whether studying TOEFL question will help students rise their test scores.

The ancestors of some French Americans originally came to The United State because of the French Revolution, that broke out in 1789.