The correct answer is E. had swum.
The sentence is in the past tense, so we need a verb
that is also in the past tense. The other options are not in the past tense.A. swims is in the present tense.
B. will swim is in the future tense.
C. would swim is the past tense of the modal verb would, which is used to express wishes, possibilities, or hypothetical situations.
D. was swimming is the past progressive tense, which is used to describe an action that was in progress at a specific time in the past.
E. had swum is the past perfect tense, which is used to describe an action that was completed before another action in the past.
In this case, Jane quit trying for the swimming team after she had swum out too far down at Horn Pond. This means that she had already swum out too far before she quit trying for the team.