Answer:
d. A letter from Clarissa
Step-by-step explanation:
In the novel Mrs. Dalloway written by Virginia Woolf. What Peter received at his hotel that causes him to reflect on his past was a letter from Clarissa.
Peter thought she must have written it immediately he left her house. Even though the content of the letter only stated that she had loved seeing him, but this annoys peter and desired that she would just forget or ignore him. Even though he knew their marriage wouldn't have lasted long but he always feel bad that Clarissa had refused him. He thought about his past by contemplating about Daisy and his way of charming women.