Question

q: if photosynthesis is a chemical process that we can’t physically see, how are we able to determine if it is occurring?
by looking for evidence such as leaf size
by measuring the plant’s roots
by measuring its by - product of oxygen and water
by looking for evidence such as how tall a plant is

Explanation:

Photosynthesis produces oxygen (and glucose, with water being an input, but oxygen is a key by - product). Leaf size, plant height, and root measurement don't directly indicate photosynthesis. Measuring oxygen (and also water - related changes or glucose production, but among the options, oxygen measurement is a valid way to detect photosynthesis as it's a by - product) helps determine if photosynthesis is occurring.

Answer:

C. by measuring its by - product of oxygen and water (assuming the third option is labeled C; if the original options had labels like A, B, C, D, and the third option is the correct one, the answer would be the option with "by measuring its by - product of oxygen and water" along with its label)