In this sentence" Indeed, no one but a veteran taxi driver knows the whole of London. "(Sent 5, Para. 1) , what does the word "veteran" mean

A．Columbia frightens urban planners.
B．Although it's very beautiful, Columbia makes young people bored.
C．Columbia is just in an urban planner' s dream.
D．There are rows of grimy buildings and few grass and trees in Columbia.

A．how animal wastes enriched land
B．how plant roots protected the land
C．how humus becomes useful
D．how a forest creates its own soil and protects the watershed