The sentence that displays correct subject-verb agreement is:
My collection of stamps is extensive.
In this sentence, "collection" is the singular subject, and "is" is the correct verb form to match it.
The other sentences have incorrect subject-verb agreement:
- "The island visited by the travelers are warm." should be "The island visited by the travelers is warm."
- "The cattle in the field is huge!" should be "The cattle in the field are huge!" (since "cattle" is plural).
- "The books at the library is very helpful." should be "The books at the library are very helpful." (since "books" is plural).