Answer:
Wait and see what happens to the plant.
Step-by-step explanation:
The best course of action for Jeremy would be to wait and see what happens to the plant after moving it closer to the window to get more sunglight.
If the plant grows after observing it for some times, he can conclude that light has been a major hindrance to the growth and more sunlight would benefit the plant. If the observation is otherwise, then Jeremy can conclude that the lack of growth observed is not due to light.