1 The National Aeronautics and Space Administration (NASA) has designed many robots to help astronauts explore space. Some robots drive around like cars, some are just large arms, and some look like humans. All of these robots can accomplish tasks in space that are too difficult or dangerous for astronauts to do alone.

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The most famous NASA robots are called the Mars rovers. According to NASA, the wheeled rovers are part of the Mars Exploration Program, “a long-term effort of robotic exploration of the red planet.” The newest rover, Curiosity, landed on Mars in August 2012. The size of a small car, Curiosity carries advanced equipment to analyze the soil and air on Mars. Curiosity has made many exciting discoveries about the planet's environment. Most importantly, it discovered that Mars contains the right ingredients to support life, including carbon, oxygen, and water. Curiosity has also found that astronauts on Mars would be exposed to dangerous levels of radiation. This discovery will help NASA protect its astronauts when they one day travel to Mars.

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NASA is also building other robots. For example, the Robonaut2 looks like the upper half of a human. The human hand is a very complex and useful tool. It might seem easy for a person to press a button, grasp and lift an object, or turn a knob, but these tasks are very hard for a robot. However, a robot that could perform these tasks would be very useful to astronauts. The Robonaut2 is now being tested at the International Space Station (ISS). Eventually, NASA wants to add legs or wheels to the Robonaut2, which would allow it to move around outside the ISS.

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Another robot on the ISS is a massive arm called Canadarm2. It can do repair work and transport objects too big for humans to move. Canadarm2 has even caught the Hubble telescope to allow astronauts to repair it. As technology develops, NASA will increasingly rely on robots. They will guide astronauts in new places, give them medical care, and do dangerous work for them. With their special equipment and considerable strength, robots can help humans explore new worlds.

Which sentence BEST explains how the author develops the central idea?

A.
He describes three different NASA robots and the work they do to support NASA.

B.
He explains how the Mars rovers are capable of important tasks like analyzing soil and air.

C.
He describes how NASA robots have human features that can do the work humans did in the past.

D.
He explains NASA's long term goals to incorporate more robotics in space exploration.

Which sentence BEST explains how the author develops the central idea?

A.
He describes three different NASA robots and the work they do to support NASA.

B.
He explains how the Mars rovers are capable of important tasks like analyzing soil and air.

C.
He describes how NASA robots have human features that can do the work humans did in the past.

D.
He explains NASA's long term goals to incorporate more robotics in space exploration.