The sentence that displays correct subject-verb agreement is "my collection of stance is extensive."
In this sentence, "collection" is the subject, and since it is singular, it correctly takes the singular verb "is." The other sentences have subject-verb agreement errors:
- "The cattle in the field is huge" should be "The cattle in the field are huge" (cattle is plural).
- "The island visited by the travelers are warm" should be "The island visited by the travelers is warm" (island is singular).
- "The books at the library is very helpful" should be "The books at the library are very helpful" (books is plural).