A、Birth. B、Environment. C、Education. D、Blood type. A根据文章中提到的“to some extent our intelligence is given to us at birth”，“it easy t

Are some people born clever and others born stupid? Or is intelligence developed by our environment and our experience? Strangely enough, the answer to these questions is yes.
    To some extent our intelligence is given to us at birth, and no amount of special education can make a genius out of a child born with no intelligence. On the other hand, a child lives in a boring environment will develop his intelligence less than one who lives in rich and varied surroundings. Thus the limits of a person’s intelligence are fixed at birth, whether or not he reaches those limits will depend on his environment. This view, now held by most experts, can be supported in a number of ways.
    It is easy to show that intelligence is, to some degree, something we are born with. The closer the blood relationship between two people, the closer they are likely to be in intelligence. Thus if we take two identical twins, they will very likely be as intelligent as each other. Relations like brothers and sisters, parents and children, usually have similar intelligence, and this clearly suggests that intelligence depends on birth.
    Imagine now that we put two identical twins in different environments. We might send one, for example, to a university and the other to a factory where the work is boring. We would soon find difference in intelligence developing, and this certainly indicates that environment as well as birth plays a part.