I think the correct answer from the choices listed above is the second option. For endothermic reactions, the reactants have less energy than the products. Which would mean that energy should be added to the reaction for it to proceed. Hope this answers the question.
Answer:

Explanation:
As we know that the 6 kg object was at rest initially
So here since net force on the system is zero
so the momentum of the system will always remains conserved
so we can say

now we know that

and the angle between the two objects is 60 degree
so we can say


now we can say that the speed of the third mass will be

now the total kinetic energy released in this system is given as



Answer:
get help with your work
try understand your work
ask your teacher for assistance or class
or maybe cheat but understand the work first if you wanna
Answer:
A spring is compressed and held at compression by a person before releasing it
Explanation:
All the other answers are showing things that are at rest and have no energy starting nor going through them. This answer show how the energy is starting and being released.