The federal courts can hear and decide cases on the basis of
a. amount of interest in the subject matter and the people affected by the case.
b. the amount of money or number of defendants.
c. diverse citizenship or human interest.
d. appeals from states and from courts of appeals.

The answer is A.

The federal courts can hear or decide cases on the basis of ammount of interest in subject matter and the people affected by the case

For example if your friend is stealing 5 dollar from you, they won't even look at it. It will be diffrent is the ammount is 100.000 dollar.