A screw has 4 threads per centimeter and a circumference of 2 centimeters. What is the mechanical advantage of the screw?

Mechanical advantage of a screw is the distance around one turn divided by the distance between threads. Four threads per centimeter means the thread spacing is 1 ÷ 4 = 0.25 centimeter. So the mechanical advantage is 2 ÷ 0.25 = 8, which is choice B, 8.

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