According to the interview, how many people have been added to the Earth’s population in the past century

A．Generator malfunction.
B．Computer error.
C．A collision with another station.
D．All the above.

A．Now, there are no wars and people live in a peaceful world.
B．More children can live to their adulthood and have their own children.
C．People live longer now than in the past.
D．People immunize many fatal diseases of which many people died.