A．The color of the dog.
B．The price of the dog.
C．Whether the dog will fit the environment.
D．Whether the dog will get along with the other pets in the house.

A．The presence of life-forms far below the Earth’’s surface.
B．The risk of infection from rare strains of bacteria.
C．Fictional representations of a hidden underground world.
D．The reliability of evidence collected by new drilling methods.