Which of these could not be used to find the mechanical advantage of an inclined plane? a. input force b. output force c. percent efficiency d. length and height of inclined plane

The first three would be needed. They take care of the fourth 1 (D). The input and output force and the efficiency are the standard ways of calculating Mechanical advantage for   simple machines. The height and length of the inclined plane is taken into account by the input and output forces and the efficiency.

D is the answer.

answer and explanation;

find the sum of the two horizontal vectors and the sum of the two vertical vectors

isoceles right angled triangle