Exploring Mars and Life on Mars

1 Elton would like to replace his current thesis. Which of the following could replace sentence 4 and better express the thesis for this essay?(E2.15A)

• A No wonder people and scientists look into the night sky and ask questions about life on this red and cold planet.

• B Yet, years of research have led scientists to confirm that Mars does indeed have a special kind of water that may support some kind of life.

• C To find life on Mars, NASA has spent millions of dollars and years of research sending unmanned space vehicles into the skies to find out what they can.

• D No change is needed for sentence 4.

2 What is the most effective way to combine sentences 6 and 7?(E2.13C)

• F Using the large, powerful telescopes located at observatories in Chile and Hawaii, scientists determined that billions of years ago, Mars held a primitive ocean as large as Earth's Arctic Ocean.

• G Billions of years ago, Mars had an ocean as large as the Arctic Ocean on Earth, and this discovery was made by scientists with the help of telescopes in Chile and Hawaii.

• H Two powerful telescopes located in Chile and Hawaii are the reasons that scientists could determine that Mars once had a large Arctic Ocean.

• J Scientists used two telescopes to confirm that Mars once had a very large and cold ocean.

3 Which sentence would best follow sentence 12 to add supporting details? (E2.15A)

• A The salts could be identified as kinds of magnesium and sodium chlorates.

• B A researcher who had worked on this project a long time identified the salts.

• C Using special equipment, researchers got enough data to prove their theories that water flowed on Mars.

• D Upon close inspection, scientists were able to see water molecules among the internal structures of the salt molecules, indicating that water was flowing on Mars.

4 Which could replace the transition Moreover in sentence 17 and create a more appropriate transition between sentences 16 and 17?

• F Meanwhile

• G However

• H For example

• J In addition

5 What is the best way to revise sentence 21?

• A Change They to The chemicals

• B Change They to The trickles of liquid

• C Change the slopes to them

• D Change the surface to it

6 Which could be added after sentence 24 to improve the clarity of the last paragraph? (E2.13C)

• F However, not every scientist is enthusiastic about life on Mars.

• G Some scientists have a wait-and-see attitude about any more possible explorations of Mars.

• H Certainly scientists and researchers for NASA are also committed to further exploration of Mars.

• J Anyone can see that the enthusiasm for finding life on Mars has not diminished in the scientific world either.