Suppose you increase your walking speed from 1 m/s to 3 m/s in a period of 1 s. what is your acceleration?
a. 2 m/s2
b. 5 m/s2
c. 4 m/s2
d. 3 m/s2

Initial speed of walking = 1 m/s
Final speed of walking = 3 m/s
Change of speed in walking = (3 - 1) m/s
                                             = 2 m/s
Time in which the change of speed occurred = 1 sec
Then
Acceleration = Change of Speed/ Time taken
                     = 2/1 m/s^2
                     = 2 m/s^2
So the correct option among all the options that are given in the question is option "A". I hope the procedure for finding the acceleration is clear to you and in future you can attempt such problems on your own and will required no help from outside.

   |acceleration| = (change in speed) divided by (time for the change)

Change in speed = (end speed) minus (start speed)

                             =    (3 m/s)  -  (1 m/s)  =  2 m/s

   |acceleration)  =  (2 m/s) / (1 sec)  =  2 m/s² .
                

Ibelieve that the correct answer is: c. along plate boundaries