Answer: I would contend that the right answer is the A) “…and at length she was able to look up with dim eyes and a smile and say..."
Explanation: Just to elaborate a little on the answer, it can be added that options C and D should be discarded, since they do not illustrate Della’s optimism - they both have a pessimistic tone. Option B does in part illustrate Della’s optimism, since she is saying that her hair will grow and she will eventually be able to use the beautiful combs, but, even though she had craved for them, she had never hoped to own them, so it is possible to contend that that does not illustrate optimism, or hopefulness. Option A is, therefore, the correct option. She got the combs that she had wanted for a long time right when she had decided to get rid of her hair, but, in spite of it, she decided to embrace them, to make them hers forever, and smiled at Jim hopefully and enthusiastically before saying: "My hair grows so fast!"