Final answer:
Mrs. Gardiner's letter implies that Darcy is deeply in love with Elizabeth, as reflected by the positive remarks and delight shown by Mrs. Bennet towards 'Mrs. Darcy'. The correct option is A.
Step-by-step explanation:
Based on the excerpt from Mrs. Gardiner's letter, it can be implied that Darcy is deeply in love with Elizabeth. The original text indicates the high regard and warm feelings that Mrs. Bennet, as well as Mrs. Gardiner, hold towards Mr. Darcy after the marriage of Elizabeth to Mr. Darcy and Jane to Mr. Bingley.
The delight and pride expressed by Mrs. Bennet visiting 'Mrs. Darcy' reflects a successful and desirable resolution, which implies that Mr. Darcy's intentions towards Elizabeth were genuine and stemmed from love.
Furthermore, the reference to 'Mrs. Darcy showcases a complete transition from Elizabeth Bennet to a married woman who is now part of Darcy's life, suggesting a deep and committed relationship.