This matter of weight is important. Man and other creatures live in a state of metabolic equiplibrium（新陈代谢的平衡）which means maintaining the body weight once a certain point has been reached. This regulation of body weight is done by thirst, hunger, and appetite.

When your blood lacks nutritional materials, this registers（记录）in the hunger center of the brain and you feel “hungry”. The body is crying out for any kind of fuel(food). And it is our appetite that sees to it hat we chooose a mixed diet, which is the kind the body needs.

1.According to this passage, a man will die _________.

A．when a certain point in losing weight has been reached.

B．when his blood lacks nutritional material

C．when his normal weight is lost

D．when he goes without food for more than 12 hours