CTAL-TA_SYLL2019 Question #51: Real Exam Question with Answer & Explanation

The Acme Elevator company uses state-transition diagrams to document the behavior of their elevator doors. The following text is taken from one of their requirements documents. Convert it into the equivalent state-transition diagram: When the doors are open, the close command starts the doors closing. When the doors are closing, the closed sensor indicates that the doors are fully closed. When the doors are closed, the open command starts the doors opening. When the doors are opening, the open sensor indicates that the doors are fully open. If the doors are closing, the open command will start the doors opening. If the doors are opening, the close command will start the doors closing. Which state transition diagram most closely represents Acme's elevator door rules?