I GIVE BRAINLIST ON ALL MY QUESTIONS Gizo Mo Warmup

During photosynthesis plants use the energy of light to produce from carbon dioxide and water glucose is a simple sugar that plants use for energy and as a building block for larger molecules a by product of photosynthesis is oxygen plants use some of the oxygen they produce but most of it is released in photosynthesis lab gizmo you can monitor the rate of photosynthesis by measuring oxygen production

observe the pane closely what do you think the bubbles are?

A) Carbon Dioxide
B) Water
C) Oxygen
D) Glucose

(YES I KNOW I DONT HAVE THE PICTURE BUT IF YOU HAVE TAKEN THIS QUESTION ALREADY PLEASE GIVE ME THE CORRECT ANSWER , thanks)