Final answer:
The statement 'Mr. Klein has not had a visitor since last Tuesday' is a fact.
Step-by-step explanation:
In order to determine whether the statement 'Mr. Klein has not had a visitor since last Tuesday' is a fact or an opinion, we need to understand the difference between the two. A fact is a statement that can be proved or verified, while an opinion is a statement that expresses someone's beliefs, feelings, or thoughts. In this case, whether Mr. Klein has had a visitor or not can be objectively confirmed through evidence or testimonies, making it a fact.