Photos means light
tropos means turning
phototropism means turning towards the light
answer is A
(gravotropizom is like gravity, if you hold that kind of plant sideways, it will try to turn sidewyas, dunno thigmatropism, helio tropizom is turning toward the sun (but ther are other light sources other than sun))
I am not sure but I think that endoplasmic reticulum is the right answer. Hope this will help.
It helps the frog adapt to certain environments as a camouflage.
By studying the environment around the people to come to conclusions on how to ease the the heat.