Answer:
B) 1.5 meters per second
Explanation:
The rate of change in Clara's speed between 10 and 60 seconds can be calculate as:

Where 
 is the mark at 60 seconds,
 is the mark at 60 seconds, 
 is the mark at10 seconds,
 is the mark at10 seconds, 
 is the 60 seconds and
 is the 60 seconds and 
 is 10 seconds.
 is 10 seconds.
Replacing values, we get:

So, the speed between 10 and 60 seconds is 1.5 meters per second