Hydroelectric dams use falling water to generate electricity. Dams affect river organisms, including the American shad, a common fish in waterways. Shad live in the ocean but swim up rivers to reproduce (spawn). Engineers have built elevators on dams for the shad and other fish. The fish swim into the elevator below the dam and are raised into the water above the dam.

Which human activity would most likely reduce the shad population?

1. preserving wetlands along the spawning areas
2. spilling chemical waste into the spawning areas
3. monitoring water conditions of the spawning areas
4. conducting fish-tagging programs within the spawning areas

Use the technical passage "New 'Time Machine' from Ice" to answer the following.

How would an increased carbon dioxide level, caused by humans, most likely affect Earth?

1. There would be more incoming sunlight.
2. There would be more oxygen in the atmosphere.
3. There would be a loss of many current environments.
4. There would be a decrease in the number of earthquakes.

Use the technical passage "New 'Time Machine' from Ice" to answer the following.

How would an increase in greenhouse gases most likely affect coastal areas?

1. Precipitation would decrease.
2. The sea level would increase.
3. Salt content of the ocean would increase.
4. The number of hurricanes would decrease.