The correct answer is (d) all of the mentioned
The explanation: Following are the advantages of the V-belt drive over flat belt drive:
a) The V-belt drive gives compactness due to the small distance between the centres of pulleys.
b) The drive is positive, because the slip between the belt and the pulley groove is negligible.
c) Since the V-belts are made endless and there is no joint trouble, therefore the drive is smooth.
d) It provides longer life, 3 to 5 years.
e) It can be easily installed and removed.
f) The operation of the belt and pulley is quiet.
g) The belts have the ability to cushion the shock when machines are started.
h) The high velocity ratio (maximum 10) may be obtained.
i) The wedging action of the belt in the groove gives high value of limiting ratio of tensions.