Official ExplanationRead the Original Sentence Carefully, Looking for Errors:
There is a problem with verb tense agreement in this sentence. If the error isn’t evident at first reading, going through the next steps will be helpful.
Scan and Group the Answer Choices:
The answer choices are different in several ways. The main differences involve the verbs used at the end of the underlined portion. (A) and (B) use “has become,” while (C) and (D) use “has been becoming,” and (E) uses “becomes.” If these differences aren’t enough to find the correct answer to the problem, you can look for other differences.
Eliminate Choices Until Only One Remains:
Logically, both parts of the sentence must be going on in the present. The genetics researchers “achieve greater success,” so the connection between genes and birth defects must also be in the present. There is no need to switch to the past tense “has become” or “has been becoming” as choices (A) through (D) do. (E) is correct.