Why is it important that blood donors have their blood counts taken?

How do ecosystem respond to nature disasters such as fires and floods

Which of the following is a cost of urbanization? a-cities can provide a high standard of living. b-cities are hubs of entertainment and education. c-paving over land changes the environment. d-job opportunities are greater in urban centers.

Factors that can increase mutation rates a. high temps b. low temps c. food additives d. uv rays