The author thinks that the conclusions of any research about people's state of mind are______.

A．Anxiety, though unavoidable, can be coped with.
B．Children's anxiety has been enormously exaggerated.
C．Children's anxiety can be eliminated with more parental care.
D．Anxiety, if properly controlled, may help children become mature.

A．People came up with the conceptual idea of a helicopter in this century.
B．Helicopters were thought to be much more dangerous than the early airplanes.
C．Chinese children were the first to experience flights in helicopters.
D．Some people thought that helicopters would develop into popular use one day.