Identify the items that are part of an ecosystem. Check all that apply.

•trees
•pond
•animals
•rocks
•mountain

Which of the following substances is not involved in the chemical reaction that pro- duces smog? a. sunlight b. particulate matter c. automotive exhaust d. ozone

Blood has traveled from the heart to the toes. which describes the next step of the circulation process?

Which element forms the basis of all organic organisms a carbon b oxygen c hydrogen d nitrogen