Consider an Old Fashioned Telephone Booth That Can Be Occupied

Multiple Choice

Consider an old fashioned telephone booth that can be occupied by one person at a time. Suppose one person went in and dialed a part of her number, and had to leave the booth. A second person went in and dialed a part of his number, and before the number was fully dialed, a connection to some other phone was made. What Java threads analogy would prevent this undesirable scenario?
I Acquire the lock prior to entering the booth
II Dial a complete number when inside the booth
III Hang up the phone and release the lock upon exiting the booth

A) I
B) I and II
C) I and III
D) I, II and III