A．establish his laboratory.
B．have a vacation.
C．visit members of his family.
D．study deafness among the families.

A．the patterns of marriage have changed.
B．many deaf people have regained their hearing.
C．most of the original population has left the island.
D．the island has become famous for its research facilities.

A．How animals survive harsh conditions in the wild.
B．How animals alter colors to match their surroundings.
C．How animals protect themselves against predators.
D．Flow animals learn to disguise themselves effectively.