Answer
d.
Work Step by Step
We know that 500 meters per second and 9.81 meters per second are not even faster than an airplane, so we can eliminate these right off the bat. 1.7 kilometers per second sounds more enticing, but it is still too slow to get into orbit. Meanwhile, 12 kilometers per second is beyond the escape speed of earth, so this is not the correct answer. (If a satellite went this speed, it would never come back.) Thus, we see that d, 4 kilometers per second, is the correct answer.
