The concept of dark matter was first proposed by astronomer Fritz Zwicky in 1933 to explain the mass missing from the Coma Cluster of galaxies. Though dark matter does not interact with light and is therefore invisible, its existence is inferred through _____ gravitational effects on visible matter, such as stars and galaxies.
Which choice completes the text so that it conforms to the conventions of Standard English?
Explanation
Context: The pronoun's antecedent is the singular "dark matter": "its existence is inferred through ___ gravitational effects" — the effects belong to dark matter itself.
Answer: A) its
Why? A pronoun must match its antecedent in number and case. Singular "dark matter" takes the singular possessive "its," parallel to the earlier "its existence."
Traps:
- B) it's → contraction of "it is"; "through it is gravitational effects" makes no sense.
- C) their → plural possessive for the singular antecedent "dark matter."
- D) there → a place word, not a possessive pronoun at all.