The detail which is an example of internal conflict in "The Monkey's Paw" is:
a. Mr. White doubts that the monkey's paw can really grant wishes.
When the Major told the story about the Monkey's paw to the White Family they didn't trust the story. It was for them a tale which can never happen in real life. The conversation between Mr. and Mrs. White regarding the Monkey's paw had a humorous approach. Their son Herbert was also excited to test the reality of the paw and become rich by making a wish from it.