Prior to Einstein, physicists once believed that the space between

Official Explanation

Read the Original Sentence Carefully, Looking for Errors:

Always pay attention to the verbs in underlined portions of GMAT Sentence Correction problems and to how the underlined portion ends. The verbs should be in the correct tense, and the underlined portion should mesh well with the rest of the sentence. Here, note the verb "would be." This use of the verb doesn’t make sense—the physicists either believed that the space was magical ether or that it wasn’t. The phrase "that constantly transmitted" works with the rest of the sentence.

Scan and Group the Answer Choices:

An initial scan of the choices reveals that only choice (A) uses the incorrect and awkward "would be." Three other choices—(B), (D), and (E)—use the simple past tense "was."

(C) uses the past perfect tense "had been." We need to look more closely at these choices to see which uses the correct past tense and also meshes well with the rest of the sentence. Eliminate Choices Until Only One Remains:

(A) can be eliminated because of the errors identified in the sentence. The use of "had been" in choice (C) is awkward. The simpler "was" is preferable.

Choice (D) correctly uses "was," but the comma and the phrase "constantly transmitted" don’t make sense with the rest of the sentence.

Choice (E) also uses "was," which is correct, but the phrase "having constantly transmitted" is awkward and does not fit with the rest of the sentence. (B) meets our demand for a sentence that uses the correct past tense and makes sense. Thus, (B) is correct.

Answer: B

TAKEAWAY: Pay close attention to the clues in the sentence that tell you what tense the verbs need to be in.