The sentence with proper subject-verb agreement is:
"Missouri and Illinois are states along the Mississippi River."
The other sentences contain subject-verb agreement errors:
- "My sister and brother are responsible for cleaning the house this afternoon." (Correct form: "are" instead of "is")
- "Hope, peace, and love are achievable for everyone." (Correct form: "are" instead of "is")
- "The members of the French Club are aware of the details." (Correct form: "are" instead of "is")