The many branches leading into the human lungs become smaller until they end in small sacs called alveoli. Each alveolus is surrounded by a net of tiny capillaries.
How does the finely branched structure of the capillary nets relate to their function in the respiratory system?
A. The branching capillaries allow the flowing blood to warm all of the surfaces of the alveoli.

B. The branching capillaries attach to the walls of the alveoli to keep them expanded and full of air.

c The branching capillaries Join bundles of alveoll together and keep them separated from other bundies.

D. The branching capillaries provide many points where the capillaries and alveoli touch and exchange gases.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.

a- all cells come from pre-existing cells

desert perennials often survive by remaining dormant during dry periods of the year, then springing to life when water becomes available. most annual desert plants germinate only after heavy seasonal rain, then complete their reproductive cycle very quickly.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.