Astudent hypothesizes that the bubbles on this water plant are oxygen gas (o2). however, identifying a gas as o2 with direct evidence requires many kinds of equipment. which observation would provide indirect evidence that the bubbles are not o2? a. the production of bubbles by the plant when it is in darkness b. a change in the size of the plant's leaves over time c. the estimated volume of all bubbles produced by the plant d. a description of the color and shape of the plant's leaves