The expression "around-the-clock" (Line 4, Para. 2) most probably means______.

A．To observe people’s attitude towards strangers.
B．To see how people get along with their friends.
C．To change people’s behavior in social life.
D．To find out how shy people are.

A．It is convenient to travel in London by underground.
B．Banks are open for the whole week except on Saturday.
C．English food is very delicious.
D．British people are friendly to strangers.