Explanation: B is an experience and doesn't give us a reason why, C is just the fact that other people have been doing it, and D is a comeback to a common objection to journal writing.
A good way of thinking about it is that A is the direct reason, and the rest is sort of supporting evidence. A would be the topic sentence in a persuasive essay, and the rest might come after it.
to contrast the concern the boys should have felt with the satisfaction they really felt.. It can be seen the boys ere very happy when the cubs boat blew up and when the cub appeared in church and was treated as a hero.