In Order That a Belt May Not Run Off the Pulley

Multiple Choice

In order that a belt may not run off the pulley

A) It should be properly tightened
B) The centre line of the belt as it approaches the pulley must lie in a plane perpendicular to the axis of that pulley
C) The belt should be provided with frictional material
D) The belt should be provided with a guide
E) None of the above