It is at rest for 3 seconds before moving at constant speed for 10 seconds.

it is at rest for 3 seconds before moving at constant speed for 4 seconds.

it is moving from 0 cm to 5 cm at constant speed of 7 cm/s.

it is moving from 0 cm to 3 cm at a constant speed of 3 cm/s.

The answer is B.

Explanation:

You're given a position vs. time graph. The the slope of the line is the change in position over time - in other words, the speed.

A positive slope indicates a positive change in position over time and therefore a positive speed. The more positive the slope, the greater the change and the greater the positive speed.

A negative slope indicates a negative change in position over time and therefore a negative speed. The more negative the slop, the greater the change and the greater the negative speed.

A horizontal slope (i.e. slope of 0) indicates no change in position over time. In other words, the speed is 0 and the object is stationary.

With this in mind, you can see the object is initially moving with a positive speed for 3 s (from t=0 to t=3), then is at rest for 3 s (from t=3 to t=6), then is moving at a (higher) positive speed for 4 s (from t=6 to t=10). You can see then that the answer is B.

A is wrong because after being at rest the object moves at a constant speed for only 4 s.

C is wrong because by the time the object gets to 5cm, it has moved at 3 different speeds (first positive slope, horizontal slope, second positive slope).

D is wrong because the object moves from 0 to 3cm in 3 s - a speed of 3cm/3s = 1cm/s.