8. The ratio of output power to input power, in percent?A. work. B. efficiency. C. horsepower. D. conductivity.

That ratio is the efficiency of whatever the power went into and came out of. There's no reason the efficiency has to be expressed as a percentage.

The ratio of output power to input power, expressed as a percentage is B. efficiency.  Efficiency is expressed as a percentage less than 100%, as a machine could never be completely efficient.