Unsupported, because we don’t know the typical level of energy produced when physicists try to fuse atoms together. We have no evidence that the physicists aren’t creating collisions with the right amount of energy to avoid splitting.

This is anti-supported, because in order to fuse together in the first place, the energy of the collision needed to overcome the repelling force.

Unsupported, because we don’t know about the relationship between the repelling force and heat. We know that if the collision produces a lot of energy, that create heat. But we don’t know what happens if the repelling force is greater or lower.

Unsupported, because we know there’s a range of energy in which two atoms can fuse and not immediately split apart. This level of energy needs to be enough to overcome the repelling force, and this could be a high level. We don’t have evidence that this is a low amount of energy.

Supported, because we know that if the energy produced by a collision greatly exceeds the minimum required to fuse, the fused atom will be very hot. The hotter an atom, the more likely it will split. I don’t like the word “likely” here, but it’s the most supported answer.