prepositions - Necessity of "in" and "the"?

Please let me know which sentence is correct. I have faced the first and third one in the Longman dictionary, but dictionaries are prone to typos and errors. So I couldn't be sure which one is correct and which one is not. Please help me know.

1. The verb is in the past tense.


2. The verb is in past tense.


3. The verb is past tense.