Magoosh Official Explanation:
Split #1: to compare one of a group to the whole group, we need the word "other". The answer choices omitting "other" make the logical mistake discuss in this post; these choices, (C) & (D), are incorrect.
Split #2: "each team" and "every team" are singular, so we need the singular pronoun "its", not the plural pronoun "their". Choices (B) & (E) make this mistake and are incorrect.
Split #3: repeated words in comparisons. The first part talk about one team's "last runner", so we can compare this to another team's last runner, or we can just compare it to "another team's". The possessive alone is sufficient to denote the second term of the comparison.
Split #4: repeating a predicate. When the same action is repeated in a sentence, we can repeat the same verb "… before any other team's can finish" or we can use the generic substitute "… before any other team's can do so." Either is correct.
Because of these splits, choice (A) is the only possible answer.