What is the main difference between Bear Paw Lake and Frog Lake as described by Dr. Bell?

• A. The main difference is Bear Paw Lake has more predatory fish.
• B. Bear Paw Lake drains at the surface while Frog Lake does not.
• C. Predatory fish can readily enter Frog Lake but not Bear Paw Lake.
• D. Bear Paw Lake is completely enclosed and does not drain, while Frog Lake is connected by a stream allowing predatory fish to enter.

Answer: (D)

The main idea being tested is how a lake’s connectivity to streams and drainage determines whether predatory fish can access it. Bear Paw Lake is described as completely enclosed and not draining, so there’s no pathway for fish to move in from outside. Frog Lake is connected by a stream, which allows predatory fish to enter. This difference in connectivity directly explains why one lake can be invaded by predators while the other remains isolated. The description that matches this mechanism—enclosed and non-draining versus connected by a stream enabling entry—is the best choice.