Yo nunca en clase. (dormir)

Yo nunca duermo en clase.

The verb "dormir" is a stem-changing verb in the present tense in Spanish. Specifically, it is an "o" to "ue" stem-changing verb in the present tense for all forms except nosotros and vosotros. Thus, when conjugating "dormir" for the first person singular form "yo," the verb becomes "duermo." Therefore, the correct fill-in-the-blank response is "duermo." The complete sentence translates to "I never sleep in class."