Which of the following is the best title for the text

A．what pain means to an animal is still not clear to human beings
B．the great development of the human fore-brain is crucial to man's experience of pain
C．the pain which animals feel can be in all aspects equated with what human beings experience
D．there are great differences in the quality, severity and emotional accompaniments in human pains

A．animals feel pain because their pupils dilate, their pulse rate and blood pressure rise
B．when body stimuli are isolated from the higher nervous centres, animals won't withdraw the stimulated limb
C．we will never know whether or not animals feel pain because they cannot speak
D．people conduct a lot of experiments on animals in order to get knowledge of pain