What is friar laurence saying?

"within the infant rind of this weak flower
poison hath residence and medicine power;
for this, being smelt, with that part cheers each part;
being tasted, stays all senses with the heart." (ii, iii, 25-28)

a. children are fragile and weak like flowers, especially romeo and his fickle love.
b. depending on the use, a single drug can heal or kill; in the same way, all things can serve a good or bad purpose
c. the best poison will always resist the most powerful medicine; in the same way, evil (death) will always triumph over good (life) in the end
d. the flower has the power to make people think with their heart instead of their head; likewise, emotions are genuine and thoughts are often artificial.