Refer to the Figure

Multiple Choice

Refer to the figure.
Medicago truncatula, or barrelclover, is a clover-like legume that has a mutualistic association with mycorrhizal fungi. In the experiment illustrated in the figure, fungi in contact with Medicago had access to either no phosphorus, or to either 35 or 700 ?M of phosphorus. According to the figure, how did Medicago alter the amount of carbohydrate it transferred to the fungi in response to the change in fungal phosphorus levels?

A) It increased its transfer of carbohydrate when the fungi contained phosphorus.
B) It decreased its transfer of carbohydrate when the fungi contained phosphorus.
C) It transferred more carbohydrate as the fungal phosphorus levels increased.
D) It ceased its transfer of carbohydrate when fungal phosphorus levels were zero.