What are two ways in which white blood cells fight pathogens that have entered the body ?

When does the circulatory system work with the respiratory system? a. during blood cell formation b. during cellular respiration c. during intestinal digestion d. during a viral infection

Explain how paleontologists use trilobite fossils as index fossils for various geologic time periods.

Select the correct answer. which of the following statements is a scientific claim? a. the early solar system had large amounts of water; so, the oldest objects in the solar system should also be abundant in water. b. the mass of the universe is much greater than current models predict; it is not possible to explain this inconsistency. c. planet earth is abundant in water, but there is no way to scientifically determine from where earth's water originated. d. earth is shaped like a sphere even if not all of the scientific observations related to its shape support this idea.