[QA] My secretary was supposed to be here at 7 o’clock, but she’s late.

Question:

My secretary was supposed to be here at 7 o’clock, but she’s late.

• A.
  My secretary arrived at 8 o’clock.
• B.
  My secretary arrived at 7 o’clock.
• C.
  My secretary should have arrived at 7 o’clock, but she didn’t.
• D.
  My secretary arrived too late to see her chief.