Final answer:
Dry, flaky, discolored skin and brittle nails are early signs of malnutrition in a postoperative lung cancer patient, while other measures like a BMI of 20 and albumin levels are not immediate indicators.
Step-by-step explanation:
An early sign of malnutrition in a patient with lung cancer who is in the postoperative period after a lobectomy could be dry, flaky, discolored skin and brittle nails. While an albumin level of 3.0 g/dL and a retinal-binding protein level of 2.0 mg/dL might indicate nutritional issues, these are not necessarily early markers of malnutrition. A body mass index (BMI) of 20 falls within the normal weight range and thus would not be indicative of malnutrition. Therefore, option B (Dry, flaky, discolored skin, and brittle nails) is the correct sign that could indicate early malnutrition.