1)Food is crushed and ground in the mouth by teeth
2)Chewed food is pushed into the pharynx
3)Food enters the esophagus
4)Food passes through a valve and into the stomach
5)Food is broken down by pancreatic enzymes and absorbed by the small intestine
6)Undigested material is pushed into the large intestine
7)Waste material is compressed in the rectum and eliminated through the anus
Answer:
12 is a tween (preteen) and still growing, definitely still a kid and not really a teen
Let say the two train cars are of masses
and 
now if the speed of two cars are
and 
then we can say that the momentum of two cars before they collide is given by

here two cars are moving in opposite direction so we can say that the net momentum is subtraction of two cars momentum.
Now since in these two car motion there is no external force on them while they collide
So the momentum of two cars are always conserved.
hence we can say that the final momentum of two cars will be same after collision as it is before collision

The amount of solid does not affect how you are describing the solid so a is the answer