Now that we are aware that asteroids cross earth’s orbit, detecting them has become important. why are they so difficult to detect if they are crossing earth’s orbit?
a. they are relatively far away. b. they are not very reflective. c. they are small. d. all of the above.

Option (D)

Explanation:

The asteroids are the rocky bodies or smaller celestial objects that are present dominantly in the asteroid belt, which is far away from the sun. This belt is present between the planet Mars and Jupiter. They are comparatively of smaller size, ranging from about a few meters to hundreds of meters and does not have a reflecting surface. Due to this, there occur difficulties in tracking them. There are millions of asteroids in the asteroid belt and are continuously moving at a speed of roughly 80,000 km/hour. There occurs frequent collision between them.

Thus, they are difficult to detect when they cross the orbit of earth.

Hence, the correct answer is option (D)- All the above.

the correct answer is c.