Size more than 2.5 cm (B): A lung nodule larger than 2.5 cm is more likely to be malignant than a smaller nodule. The size of the nodule is a significant factor in determining the likelihood of malignancy, with larger nodules having a higher probability of being cancerous.

High serum calcium (A): Hypercalcemia can be associated with malignancies, particularly squamous cell carcinoma of the lung, due to paraneoplastic syndromes. However, it's also seen in other conditions, including hyperparathyroidism and vitamin D intoxication.
Patient age (C): While age is a risk factor for lung cancer, with incidence increasing significantly after the age of 50, a 30-year-old patient is less likely to have lung cancer compared to an older individual. However, it's not entirely indicative on its own without considering other factors.

Lung Cancer with Paraneoplastic Syndromes: Conditions like hypercalcemia (as mentioned) or other paraneoplastic syndromes can be the first presentation of an underlying malignancy. Missing these could lead to delayed diagnosis and treatment.
Tuberculosis: Although the question aims to differentiate from tuberculosis, it's crucial not to miss TB, especially in regions with high prevalence, as it requires specific treatment.

Other Malignancies: Rarely, lung nodules can be metastases from other primary cancers or represent rare primary lung tumors such as carcinoids or lymphomas.
Granulomatous Diseases: Besides tuberculosis, other granulomatous diseases like sarcoidosis or histoplasmosis can present with lung nodules, though they are less common and typically have additional clinical features.