I think it's A. focus each paragraph on one main idea. I hope this helps if it's the wrong answer I'm sorry.
The first gap is best filled with "resembled" (Sebastian comments here that many people believed that his sister was similar to him in the looks)
The second gap is "remembrance" - he means here that he cries after her (the more refers to more salt water, that is his tears)
is improving,was Improving,had been improving, will have been improving
