Hi. The answer of this question is (a) - he thought the boys would prefer to keep their secret.From the story:
I waited outside until the boys rejoined me, then drove them back to the city. They sat
beside me, not speaking. For my part, I did not say a word — I knew they would prefer to
feel that they had safely kept their secret. Yet their devotion had touched me deeply.
War had not broken their spirit. Their selfless action brought a new nobility to human life,
gave promise of a greater hope for human society.