Which statement is correct?

the number of electrons of a neutral atom always equals the number of protons.
the number of neutrons always equals the number of protons.
the number of neutrons always equals the number of electrons.
atomic weight is identical to atomic mass.

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.

Each hereditary trait corresponds to

When you run, you begin to breathe heavier and faster. your heart beats more quickly, bringing more oxygen to your cells. which organ systems are working together here?