What would happen if there were no carbondioxide in the air ?

Which of the following would be the best hypothesis for this experiment? a) use of the ginko biloba extract improves clinical outcomes when administered to patients with t2d. b) ginko biloba improves clinical outcomes of diabetes patients when combined with metformin. c) diabetes in patients is worsened when ginko biloba is taken in conjunction with metformin. d)the use of ginko biloba to treat t2d in combination with metformin lowers the cost of t2d treatment. ginko biloba shows benefits against t2d when combined with plant extracts as compared to other treatments.