It is a strange question on a book.
Give an example of a tree $T$ that does not satisfy the following property: If $v$ and $w$ are vertices in $T$, there is a unique path from $v$ to $w$.
I think it is rather strange because a tree $T$ is defined to be a simple graph and if $v$ and $w$ are vertices in $T$,there is a unique simple path from $v$ to $w$. Maybe the answer is the difference between "path" and "simple path"? Thanks for your help.
ps: It is the 39th exercise in 7.1 Exercises of the book Discrete Mathematics (Fifth Edition) written by Richard Johnsonbaugh.