An old man with steel-rimmed spectacles and very dusty clothes sat by the side of the road. There was a pontoon bridge across the river and carts, trucks, and men, women and children were crossing it. The mule-drawn carts staggered up the steep bank from the bridge with soldiers helping to push against the spokes of the wheels. The trucks wound up and away heading out of it all. The peasants plodded along in the ankle-deep dust. But the old man sat there without moving.
The mule-draw carts stagered up because,

Options

A. there were too many mule-carts
B. the mules were indisciplined
C. it was a steep uphill journey
D. the carts were blocked by the peasants