The tone of the passage can best be described as ______.

A．forgetting for lack of practice tends to be obviously inadaptive
B．if a person gets very forgetful all of a sudden he must be very adaptive
C．the gradual process of forgetting is an indication of an individual's adaptability
D．sudden forgetting may bring about adaptive consequences

A．he would survive best
B．he would have a lot of trouble
C．his ability to learn would be enhanced
D．the evolution of memory would stop