It's number three on your worksheet. ;)
The difference between temperature and thermal energy is that temperature measures the average kinetic speed of molecule and thermal energy is the total kinetic energy of all particles in a given substance.
Answer:

Explanation:
As we know that there is no external torque on the system of two disc
then the angular momentum of the system will remains conserved
So we will have

now we have

also we have

now from above equation we have

now we have


You should come off like would you like to hang out sometime
Nuclear fission is seperating an atom so product is b.
Energy is released during nuclear fussion. Mass is converted into energy because E=mc^2, this is the energy that is released