Final answer:
The correct option to complete the sentence with the provided choices is (c) 'can't,' yet it changes the positive sentiment of the original sentence, leading to a contradiction. Proper grammar would require another form of rephrasing to maintain the original meaning.
Step-by-step explanation:
The sentence "What a good time she'll have learning to swim!" is an exclamatory sentence expressing enthusiasm about the prospect of someone learning to swim. Good grammar requires that we maintain the exclamatory structure in completing the sentence. The correct option to complete the sentence is (c) can't, resulting in: "What a good time she can't have learning to swim!"
However, this sentence seems to contradict the positive sentiment originally expressed. If it is intended to keep the sentiment positive, then the sentence should not be completed with any of the provided options, as they change the meaning. The correct completion without changing the meaning would potentially involve rephrasing the sentence entirely, which is not an option given here.