**Core Concept:** Vocabulary (Phrasal Verb Usage). **Analysis:** The phrase 'rake in' specifically means 'to earn or gain a large amount of something, typically money.' Option A correctly uses it in the context of earning profits. Option B misapplies the phrase to physical objects (textbooks), which is incorrect. Option C uses the literal meaning of 'rake' (a gardening tool) but not the phrasal verb 'rake in.' Option D incorrectly applies it to abstract ideas, which is unsupported by standard usage. **Key Clue:** The collocation 'rake in + profits' aligns with the idiomatic meaning. **Common Pitfall:** Confusing the literal meaning of 'rake' with the phrasal verb 'rake in.'