If CFCs have not been widely used since the late 20th century, why are they considered a major greenhouse gas in the 21st century?

__can be defined as which velocity changes

The image compares the arrangement of electrons in two different neutral atoms. a figure labeled atom q has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has six black spheres. to the left of this figure is another figure labeled atom p. atom p has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has seven black spheres. which of the following best explains the position of the two atoms in the periodic table?

Which can be observed only in a microscopic view? a) structure of a muscle cell b) shape of a soybean plant c) foam insulation d) x-ray of a knee joint