How have conditions for life on earth changed over time?
a.
separation of continents
c.
both a and b
b.
ice age
d.
neither a nor b

The large increase in atmospheric carbon dioxide in the last 50 years most likely comes from a. an increase in cellular respiration b. increased decomposition by bacteria c. an increase in the burning of fossil fuels d. an increase in photosynthesis

What is the primary function of the nervous system?

What type of reaction is photosynthesis