Answer:
Option a. 100 meters.
Explanation:
A bus moves away from bus stop in a straight line. After 1 second it was 10 meters away, after 2 seconds it was 20 meters and after 3 seconds it was 30 meters away.
In this way bus forms an arithmetic sequence
10, 20, 30, 40........up to 10 terms.
nth term of an arithmetic sequence is represented by

Here a = 10 and d = common difference = 10
Therefore 10th term = 10 + (10-1)10 = 10 + 90 = 100
Therefore after 10 seconds bus will be 10 meters away from the bus stop.