Aball rolls down a hill and hits a box. the momentum of the ball decreases. which happens to the momentum?

select one of the options below as your
a. it is transferred to the box.
b. it is converted to inertia.
c. it is converted to mass.

First let us examine our options. For B, the law of inertia state that an object will keep on moving unless acted upon an external force. And I am thinking this is not the appropriate answer here. Also for C momentum and mass are not the same. Momentum is energy. Momentum cannot be converted to mass. A is the answer since momentum. When the ball hits the box, the box will move and decreases the velocity of the rock. Here momentum is transferred. 

This is the answer of your question