CO2 + H2O → C6H12O6 + O2

Iwould you figure it out but you don't have a picture or in your question as to what the physical property you're looking for is

There is no reason to think the results are biased or not conducted properly but you should not assume the results are correct just because they were done in a laboratory so the answer would be c. it is likely to be reliable because the results support the conclusion presented.