Step 1: Understanding the Concept:
This question is from the chapter "A Letter to God" and asks about the specific quality of the protagonist, Lencho, that moved the postmaster.
Step 2: Detailed Explanation:
In the story, when the postmaster reads Lencho's letter addressed to God, he is initially amused. However, he soon becomes serious. He is deeply impressed by the writer's unshakable faith. The postmaster exclaims, "What faith! I wish I had the faith of the man who wrote this letter." He decides to answer the letter to preserve this faith. Therefore, it was Lencho's great faith in God that impressed him the most.
Step 3: Final Answer:
The quality that impressed the postmaster was Lencho's profound faith. Thus, the correct option is (B).