The parts of the model shown here illustrate the levels of organization found in the human respiratory system. Number the parts from 1 to 4 to show the correct order from the simplest to the most complex.

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.

gas

explanation:

smoke is the matter of a gas

level 4 to level 2 : ))