What is the difference between placer mining and hard rock mining (lode mining)?

What is the difference between placer mining and hard rock mining (lode mining)?

• A. Placer mining extracts free gold from sediments; hard rock mining extracts gold from ore embedded in rock.
• B. Placer mining uses chemicals; hard rock mining uses gravity separation.
• C. Placer mining extracts gold from ore embedded in rock; hard rock mining extracts free gold from sediments.
• D. Placer mining is for silver; hard rock mining is for gold.

Answer: (C)