Step 1: Potency selection depends on the nature and depth of the disease. For sudden, short-lasting acute conditions, a moderate potency is safe.
Step 2: For acute diseases like fever or cold, 6C or 30C is commonly given.
Step 3: Higher potencies (200C, 1M) are preferred for deep chronic or constitutional cases. Q potency (Mother tincture) is used for organ support, not acute prescribing.
Hence, the correct choice is (D) 30C.