What does it mean when there is variation within a species?

Which would happen if more forests were cut down? a. the nitrogen cycle would be stopped b. nitrogen would be fixed by bacteria more quickly c. the amount of co2 in the atmosphere would increase d. fossil fuels would build up in the soil c the amount of co2 in the atmosphere would increase

The terrestrial planets are characterized by having a a.) silicate core b.) iron-rich silicate core c.) iron-rich metallic core d.) none of these

18. which statement about cancer is true?