Digital PSAT Reading and Writing Practice Question 64: Answer and Explanation

Question: 64

Following physicist Carl D. Anderson's 1932 gamma ray ______________ anticipated the discovery of negatively baryon-charged antimatter throughout the universe in quantities that would precisely counterbalance the positive baryon charge of matter.

Which choice completes the text so that it conforms to the conventions of Standard English?

  • A. experiment which demonstrated the existence of antimatter, scientists
  • B. experiment, which demonstrated the existence of antimatter, scientists
  • C. experiment; which demonstrated the existence of antimatter, scientists
  • D. experiment which demonstrated the existence of antimatter scientists

Correct Answer: B

Explanation:

(B) The sentence can still function as a complete sentence without the phrase "which demonstrated the existence of antimatter," so it is appropriate to use commas to set it aside. Choice (A) does not have a necessary pause before the phrase, choice (C) does not have the necessary completed sentence before the semicolon, and choice (D) has no pauses whatsoever.

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