Lidia plans an experimental investigation to see how the thickness of a lens affects the point where a beam of light is focused. She plans to shine light through a lens and measure the distance to a screen that is placed where the beam focuses. What are the controls in Lidia’s investigation?

How did different parts of the united states feel about slavery

The graph shows a trend in an ecosystem over time caused by increased pollution in the region. what can you conclude from the graph? a. there’s lower biodiversity among birds. b. there’s a higher reproductive rate among birds. c. there’s a significant decline in the number of producers. d. other types of animals were unaffected by pollution.

An ecosystem is shown in the illustration. assume that human activities have led to a decrease in the number of eagles. a virus attack on rabbits has led to a decrease in their population in the ecosystem. which two sentences describe likely effects on the ecosystem? 1. there’s an increase in the number of snakes and insects and a decrease in the number of frogs. 2. there’s an increase in the number of snakes and insects, and the storks face increased competition for food. 3. there’s an increase in the number of storks and a decrease in the number of snakes and insects. 4. there’s an increase in the number of frogs and a decrease in the number of storks and insects. 5. there’s a decrease in the number of snakes, insects, and frogs.