Native Americans had taken care of these precious natural resources wisely. Unfortunately, it took the explorers and the settlers who followed only a few decades to decimate a large part of these resources. Millions of waterfowl were killed at the hands of market hunters and a handful of overly ambitious sportsmen. Millions of acres of wetlands were dried to feed and house the ever-increasing populations, greatly reducing waterfowl habitat.What was a cause of the waterfowl population decline in North America? A．Loss of wetlands. B．Popularity of water sports. C．Pollution of rivers. D．Arrival of other wild animals.

【题文】   When the explorers first set foot upon the continent of North America, the skies and lands were alive with an astonishing variety of wildlife. Native Americans had taken care of these precious natural resources wisely. Unfortunately, it took the explorers and the settlers who followed only a few decades to decimate a large part of these resources. Millions of waterfowl were killed at the hands of market hunters and a handful of overly ambitious sportsmen. Millions of acres of wetlands were dried to feed and house the ever-increasing populations, greatly reducing waterfowl habitat.

What was a cause of the waterfowl population decline in North America?

A．Loss of wetlands.	B．Popularity of water sports.
C．Pollution of rivers.	D．Arrival of other wild animals.