The Russian physiologist Ivan Pavlov found that sounding a bell every time a dog was about to be given food eventually caused a reflex flow of saliva, which later persisted even when no food was produced. Elaborations of this habituative type of reflex are regarded by some physiologists and psychologists as an important basis for many behaviors, both voluntary and involuntary.
Q.What is the style of the passage?
A.informal
B.sarcastic
C.scholarly
D.humorous