None of these.

As no staff member entered at 14:00 hrs, no staff member could have left at 17:00 hrs (after 2 hrs). Hence (b) is not true.

As no devotee entered at 15:00 hrs, no devotee could have left at 17:00 hrs (after 2 hrs). Hence (c)is not true.

If at 15:00 hrs, 1 staff member and 1 priest entered, then 1 staff member left at 17:00 hrs (after 2 hrs).

If at 15:00 hrs, 2 staff members entered, then 2 staff members left at 17:00 hrs (after 2 hrs). Hence (a) may or may not be true.

Hence, none of these options.