Perfect machine is not possible in real life, why?​

A perfect machine is not possible because perfect machines mean that the system will always perform at a 100% efficiency, and that's not possible in real life because the systems of the real world will always lose some energy in the form of heat, resulting in a lower efficiency percentage.

i think the answer is a, hope this : )

part 1: which substance has a higher solubility?

a

smallest amount left undissolved atall temps in table shown most has dissolved high sol'by