[单项选择]That experiences influence subsequent behaviour is evidence of an obvious but nevertheless remarkable activity called remembering. Learning could not occur without the function popularly named memory. Constant practice has such an effect on memory as to lead to skilful performance on the piano, to recitation of a poem, and even to reading and understanding these words. So-called intelligent behaviour demands memory, remembering being a primary requirement for reasoning. The ability to solve any problem or even to recognize that a problem exists depends on memory. Typically, the decision to cross a street is based on remembering many earlier experiences. 　　Practice (or review) tends to build and maintain memory for a task or for any learned material. Over a period of no practice what has been learned tends to be forgotten; and the adaptive consequences may not seem obvious. Yet, dramatic instances of sudden forgetting can be seen to be adaptive. In this sense, the ability to forget can
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