A By weighin each pot
B By looking at the pot
C Measuring amount of water that drained from pot
D Plant seed in pots
I’m not 100% sure, but my guess would be C.
Answer this by the process of elimination. What will you find if the weight of each pot is the same? nothing. If different, then there is more soil in one pot than the other one. By looking at the pot? Looking may give you a close answer but it isn’t very scientific. Draining water from the pot will tell you how much water is held up by the soil. Planting seeds in the pot will grow plants. Now, which of these answers is what you want?