Keep a green tree in your heart and perhaps a singing bird will come
A
Correct answer
Explanation
This is a proverb suggesting that maintaining hope and positivity (keeping a green tree in your heart) attracts good things (a singing bird). In the context of proverb/wisdom literature, this is treated as a true statement of philosophical wisdom rather than a factual claim to be verified scientifically. The answer key identifies this as a correct proverb.