After teaching a client who has diabetes mellitus and proliferative retinopathy, nephropathy, and peripheral neuropathy, the nurse assesses the client's understanding. Which statement made by the client indicates a correct understanding of the teaching?
a. "I have so many complications; exercising is not recommended."
b. "I will exercise more frequently because I have so many complications."
c. "I used to run for exercise; I will start training for a marathon."
d. "I should look into swimming or water aerobics to get my exercise."