What effect would a current of greater than 0.2 amp have on your body? a. it would be almost unnoticeable. b. it might cause an irregular heartbeat and disrupt the flow of blood. c. it could cause burns and stop your heart. d. it would feel like a shock you get from touching a doorknob.

-- b). It could cause an irregular heartbeat and disrupt the flow of blood.

-- c). It could cause burns and stop your heart.

-- By flowing through any nerve, it could cause strong contraction
of any muscle controlled by that nerve ... possibly strong enough
to break any bone connected to that muscle.

-- It would not take nearly 0.2 amp to have these effects. 
I have read that a current of 0.015 amp is enough to do it,
if it flows through the right soft, juicy parts of the body.

The independent variable would be the fertilizer as it is what the dependent variable (the growth of grass) depends on.