An artificial satellite orbiting the earth does not fall down because of the earth's attraction:
A) Is balanced by the attraction of the moon.
B) Vanishes at such distances.
C) Is balanced by the viscous drag produced by the atmosphere
D) Produces the necessary acceleration of its motion in a curved path.

Hint: Artificial satellites are built by humans and sent into space for various purposes. It helps us collect data about the space, helps in predicting weather, get satellite images of the earth, etc. They are sent with high velocities into space so as to avoid earth’s gravitation while travelling to space. Once they reach in space, there are a number of forces acting on it.

Complete answer:
Artificial satellites are sent into space for a range of missions that may be scientific research, weather observation, military support, navigation, Earth imaging, communications, etc. Some satellites are sent into space for some specific missions, like earth imaging, or navigation, while others can fulfill more than one objectives at the same time. Equipment on a satellite is hardened to survive in the radiation and vacuum of space.

We usually feel weightless in satellites. This feeling of weightlessness happens because the net magnitude of force on our body is almost equal to zero. This is because the earth's gravitation is cancelled out in terms of magnitude by centrifugal force by the satellite.

But on the other hand, the earth’s gravitational force of attraction is necessary in order to change the direction of the satellite continuously and thus providing the acceleration in terms of the change in direction of the satellite.

Therefore, option D is the correct answer to this question.

Note: When artificial satellites are sent into outer space, a huge velocity is given to them to escape the earth’s gravitation completely. At that point, they develop their own velocity and acceleration, with respect to the other forces acting on them so they move in a path in correspondence to earth’s revolution around the sun.