Explanation

Creating a filter: in this question, in the underlined portion, something is off with the verb "was." We are talking about what would prevail in the past under a condition specified by the word "if," so we need the conditional tense - we need a "would" word. In other words, "if they had given that up, they would have been doomed." We go to the answer choices in search of the conditional tense.

Applying the filter: (B), (D), and (E) have the conditional tense we are looking for.

Finding objective defects: choice (D) conveys a sense contrary to the intended meaning. They aren't shaky - like, scared or something - their footing is. The word order in (E) is inferior; the word "shaky" is far from "footing" and far from "forever," and it wants to be close to words it's related to. In (E), moreover, the word "that" at the end is far from its referent. Choice (B) is clearer and better English idiom. The correct answer is (B).