The word "paradox" ( Para. 1 ) means" ______ ".

A．theories of its origin and history are varied
B．our knowledge of it is highly insecure
C．only a very. small sample of it has been observed
D．few scientists are involved in the study of astronomy

A．it is not based on personal experience
B．new discoveries are less likely to occur in social sciences
C．it is based on a fairly representative quantity of data
D．the records of social systems are more reliable

A．The men in Samoa were not quite blind.
B．A girl called Virginia could read newsprint even when she was blindfolded.
C．Rosa' s ability to see was confined to her fingers.
D．The result of the last test on Rosa was least doubtable.