Based on the context of the question and the process being discussed, Charlie would likely be able to answer the following question using the diagram:
a. What is the ratio of glucose and water created through cellular respiration?
This question pertains to the outputs of cellular respiration, which is suggested to be the focus of the diagram Charlie is viewing. The other questions relate to different processes (photosynthesis) or aspects (storage of glucose and water) that may not be directly related to the diagram of cellular respiration.