It is possible that the exercise has a typo. However, there are logics that construe its claim as correct. Tautologies are logically true, by logic alone, it is a linguistic notion. Necessity, on the other hand, is a modal notion, and a priori is an epistemological notion. There is no conceptual reason why the three can not come apart. This said, contingent tautologies are quaint, and logicians rarely entertain them, even Kripke explicitly stipulates that he only considers analytic truths, which includes tautologies, that are necessary. However, Kaplan's sentence "I am here now" can be construed as a contingent tautology, it is tautologically true in any utterance, but it could always have been otherwise.
In Demostratives Kaplan suggests that the distinction between logical and necessary truths reflects the distinction between character and content:
"The bearers of logical truth and of contingency are different entities. It is the character (or, the sentence, if you prefer) that is logically true, producing a true content in every context. But it is the content (the proposition, if you will) that is contingent or necessary".
An alternative path to contingent tautologies is to allow logic itself to vary across possible worlds. In worlds where the classical logic obtains the law of excluded middle will be a tautology, but not in intuitionistic worlds. Thus, the law of excluded middle will not be a necessary tautology. Zalta discusses more examples in Logical and Analytic Truths That Are Not Necessary.