Read the following passage and mark the letter A, B, C, or D to indicate the best answer to each of the questions.

For many years, scientists and space fans have been excited about the idea of living on Mars. The Red Planet, with its rocky land and thin air, is the most Earth-like planet in our solar system. However, turning Mars into a place where humans can live brings colossal challenges.

The first big problem is the difficult Martian environment. [A] Unlike Earth, Mars has no magnetic field to protect it from dangerous solar radiation. [B] Also, the average temperature on Mars is very cold, about -60 degrees Celsius. This means any future homes must be well-covered and heated. [C] The air is mostly carbon dioxide, so it is impossible for humans to breathe without special equipment. [D]

Even with these big problems, new technology is making the dream of living on Mars come true. Organizations like NASA and private space companies are finding new ways to help. For example, researchers are looking for ways to get water from ice under the ground. This water could be turned into oxygen to breathe and fuel for rockets. They are also making 3D-printed homes with Martian soil to protect the first people from radiation and very cold temperatures.

If humans successfully build a home on Mars that can take care of itself, it will be a very important step. It will not only help humans survive if something bad happens on Earth but also help us explore other parts of the solar system. While it may take many more years, the idea of living on different planets is very possible today.

Mark the letter A, B, C, or D on your answer sheet to indicate the word(s) CLOSEST in meaning to the...