It is very long journey. I guess he sleeps all the way to Mount Abu.

Explanation-In future continuous tense we use Will/shall + be + v1+ing, as we know will and shall represent the probable action for the future time and they are also modals. So, with modals we use base form of the verb so we use ‘Be’ with will and shall and to make it continuous we use V1+ing. Therefore, Will be sleeping is correct. So option (B) is correct.