A gymnastics instructor is planning a weekly schedule, Monday through Friday, of individual coaching sessions for each of six students—H, I, K, O, U, and Z. The instructor will coach exactly one student each day, except for one day when the instructor will coach two students in separate but consecutive sessions. The following restrictions apply:
H's session must take place at some time before Z's session.
I's session is on Thursday.
K's session is always scheduled for the day immediately before or the day immediately after the day for which O's session is scheduled.
Neither Monday nor Wednesday can be a day for which two students are scheduled.
Which one of the following must be true?