Which term refers to a change in the environment that causes an organism to take action? a. growth b. genetics c. response d. stimulus

(D) stimulus is the answer 

D Stimulus 
stim·u·lus[ˈstimyələs]NOUNstimuli (plural noun)a thing or event that evokes a specific functional reaction in an organ or tissue: "areas of the brain which respond to auditory stimuli"a thing that rouses activity or energy in someone or something; a spur or incentive: "if the tax were abolished, it would act as a stimulus to exports"synonyms: spur · stimulant · encouragement · impetus · boost · prompt · prod · incentive · inducement · inspiration · motivation · impulse · shot in the armantonyms: deterrent · discouragementan interesting and exciting quality: "she loved the stimulus of the job"

Answer : option a) 84explanation :

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.