One twelfth the mass of a carbon-12atom is used to define a.

a weighted average of the masses of an element isotopes. One twelfth the mass of carbon-12 atom is used to define a. atomic mass unit.

introduction of a drug directly into the respiratory tract is a form of inhalation administration.

why is arctic sea ice important? arctic sea ice keeps the polar regions cool and moderate global climate. sea ice has a bright surface; 80 percent of the sunlight that strikes it is reflected back into space. as sea ice melts in the summer, it exposes the dark ocean surface.