The correct answer is C) A force acting through a distance. Mechanical work is defined as the product of a force and the distance over which that force is applied. This is in accordance with the basic physics formula for work: Work = Force x Distance. Option C correctly captures this definition of mechanical work. The other options are incorrect because they do not accurately describe the definition of mechanical work. Option A refers to pressure, option B refers to power, and option D refers to speed or velocity, none of which are the correct definition for mechanical work.