Aid in the immune system to fight infections.
a. red blood cells
b. platelets
c. arteries
d. white blood cells

Consider the model of the oxygen cycle on earth. the majority of earth's oxygen reservoirs are found in the a) atmosphere. b) biosphere. c) hydrosphere. d) lithosphere.

State officials are considering constructing a road through a forested wilderness area. this action will likely affect the forest ecosystem in various ways. part a: predict how the construction of a road could negatively affect plants and animals in that ecosystem. (3 points) part b: describe one way that the construction of a road could have a positive impact of the forest ecosystem. (1 point)

Which worm has eyespots that are used to detect light? a fluke b marine worm c planarian d tapeworm