A. down
B. by
C. out
D. None of these
🧠 Explanation:
In the phrase "Put _ something for rainy day," the preposition "by" completes the idiom "put by," meaning to save for future needs. Idioms like this convey practical advice, common in financial or planning contexts. Proper preposition use ensures clarity, enhancing communication. This example underscores the importance of idiomatic expressions in English, vital for fluency in writing or speaking, particularly when discussing preparation or resource management in personal or professional settings.
