Which country were the first to add sugar to their cocoa drink

A．It reduces pain and stress.
B．It contains substances called flavonoids.
C．It releases endorphins in human body.
D．It acts like aspirin to protect heart.

A．why office doors were often left open
B．when it was a good time to turn off the computer
C．what questions office workers were bothered with
D．which behaviors could tell whether a person was busy