Final answer:
The mechanical advantage of gear D is 2, as its diameter is twice that of gear C. Therefore, gear C will make two revolutions for every one revolution of gear D.
Step-by-step explanation:
The question is asking about the mechanical advantage of gear D in relation to gear C when D has twice the diameter of C. Mechanical advantage in gears is calculated based on the ratio of the diameters of the gears; in this case, since gear D has twice the diameter of gear C, gear D has a mechanical advantage of 2. The mechanical advantage indicates how much the force is multiplied when transferred from one gear to the other. Additionally, because gear D has twice the diameter, it will make half as many revolutions as gear C for every full rotation of gear C. Therefore, the correct answers are: (c) The mechanical advantage of D is 2, and for every one revolution of gear D, gear C will make two revolutions.