Which of the following describes how Earth's atmosphere changed during Precambrian time? A. The amount of carbon dioxide increased.
B. Torrential rains never reached the surface until the Paleozoic era.
C. The amount of oxygen increased.
D. Precambrian oxygen was quickly used up by plants.

The influenza virus cause the flu, but not other diseases. why?

African penguins, which inhabit the coasts of southern africa, were classified as an endangered species in 2010. two significant threats to their survival are ecosystem damage from oil spills and overfishing by humans. overfishing depletes the food supply of african penguins. the best method to reduce the threat of overfishing would be to . the risk of oil spills could be reduced by increasing the use of , which should oil consumption. if an oil spill does occur, could be used to remove the oil so the ecosystem may more quickly recover.

Which type of respiration takes place when there is no oxygen present? a. anaerobic b. mitochondrial c. cellular d. aerobica. anaerobic