A、Part of a textbook. B、A large chart. C、A recent research. D、Part of a science fiction. A讲话者在该篇开头、结尾都提到了“chapter”一词，并询问大家是否有问题，

There are many kinds of nerve cells, and this chapter deals mainly with three kinds. The sensory nerve cells carry messages her heat, light, sound and pressure from the skin, muscles and organs inside the body.  Motor nerve cells carry messages to the muscles, and this causes the muscles to move. Connecting  nerve cells go between the sensory nerve cells and motor nerve cells. After the messages go from the spinal cord to the brain, the brain sends messages through the motor nerve cells to the muscles. All these different nerve cells help us to see, hear, taste, smell and feel.
    Now if you have no further questions about chapter seven, we’ll go on to talk about the chemical processes involving the transfer of messages.