Birds have a system of and that serve to exchange gases.
a. spiracles; lungs
b. air sacs; spiracles
c. air sacs; lungs
d. gills; lungs
e. gills; spiracles

Describe how an electric generator works

What is the surface temperature of the ocean where hurricanes form? greater than 80 celsius approximately 27 celsius at least 76 celsius less than 10.5 celsius

Students in biology are studying the macromolecules of life. they used a calorimeter to determine the calories in various types of food. once the lab was completed, the students ate the left over food samples. monica commented that in just 6 or 7 "chews" of the saltine, it was gone; nothing but a sticky paste in her mouth. elaborate on what happened chemically while chewing the saltine. include the macromolecules present.