A patient with chronic obstructive pulmonary disease (COPD) reports having off-and-on symptoms of dyspnea, coughing, and sputum production. The patient's FEV1/FVC is 65% of the predicted value, and the FEV1 is 55% of the predicted value. Which level of COPD severity does this patient have?

a) Mild
b) Moderate
c) Severe
d) Very severe