Question

would an observational study be the best way to prove that kale grows better under a grow lamp vs. sunlight? yes, assuming youre able to limit enough variables. no, because the grow lamp is an independent variable. no, your observation of the plants will skew the results. yes, if you change nothing after the study has begun.

Explanation:

An observational study may not be the best way as it is difficult to control all variables. In an observational study, there could be many confounding factors that affect the growth of kale under grow - lamp or sunlight. For example, differences in temperature, humidity, soil quality etc. that cannot be fully controlled just by observation. An experiment where variables can be more precisely manipulated and controlled would be better.

Answer:

No, because the grow lamp is an independent variable and an observational study is not sufficient to isolate the effect of the grow lamp versus sunlight while controlling for other variables. So none of the given options are completely correct, but the idea that observational study is not ideal due to variable - control issues is key.