In a perfectly efficient machine, the work output
work input.
A) is independent of
B) is equal to
C) is greater than
D) is less than

(B) Is equal to

Explanation:

The work we do on a machine is called work input. We apply a force called the input force to the machine and move it through a distance. The work done by the Machine is called work output. The machine applies a force called the output force through a distance.  

When a machine changes the size of the force, the distance through which the force is exerted must also change. Force or distance can increase but not together. When one increases the other must decrease. This is because the work output is never greater than the work input.

Mechanical efficiency is a comparison of a machine's work output with the work input.  

Mechanical efficiency = work output/work input x 100  

No machine is 100 percent efficient, but reducing the amount of friction in a machine is a way to increase its mechanical efficiency.  

If a machine could be made that had 100 percent mechanical efficiency, it would be called an ideal machine where the work input is equal to work output.

there are no correct statementd on the list of choices you provided.

when heated, the valance electrons increased their speed and transferred the heat from electron to electron.   i just took the test.