We are having our dinner ______ suddenly someone knocked the door.

A．They should be highly skilled and at the cutting edge in their professions.
B．They should keep updating and expanding their knowledge.
C．They should work at home isolated from the outside world.
D．They should be students throughout their entire professional life.

A．Thanks.
B．Yes, it is wonderful time.
C．Fine. And you
D．I’m glad to see you too.