What feature of alveoli adapts them to efficient gas exchange?
a. they have muscles which pump air in and out regularly.
b. their membranes are more permeable to gases than water.
c. a constant blood supply flows through them.
d. a dense network of capillaries surrounds them.

Which sequence correctly shows the path of carbon dioxide during repiration?

This is a typical grassland food web. it is also a small picture of an important cycle on earth: the carbon cycle. describe how the carbon gets into this food web. a) bacteria and fungi, the decomposers, recycle carbon from dead organisms. b) carbon is found in the grass and is passed from one level to the next in this food web. eliminate c) all living things give off carbon dioxide as a by-product of respiration and it is released into the atmosphere. d) plants use carbon dioxide as a reactant in photosynthesis, to make usable chemical energy in the form of a sugar.

Communication and transportation have improved as a result of scientific advancements. select the best answer from the choices provided of mark this and return save and exit next