The reactivity of an atom arises from
a. the average distance of the outmost electron shell from the nucleus.
b. the existence of unpaired electrons in the valance shell.
c. the sum of the potential energies of all the electron shells.
d. the potential energy of the valance shell.

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.

i believe your answer would be c.. : )