What does blood do for us? It brings food to all parts of our bodies and takes waste away from them．All parts of our bodies are made of cells（细胞）．These cells are very small．They all need food all the time．No one had seen cells before the invention of microscope．No one could make pictures of cells because no one could see them．
What makes the blood move round the body? The heart does．The heart is a pump．It pumps the blood and sends it round the body．The heart has rooms with doors between them．It pumps blood in and out through these doors by changing the size of the rooms so that the doors are opened and shut．The heart keeps a stream of blood going all around the body and back again to itself．The heart is a very important part of one’s body．When it stops beating，one will die．
1．Blood is important to our body because it can ________．
A．provide pictures of cells B．bring food and take waste
C．form a stream D．move around the heart
2．What does the underlined word“microscope”mean in Chinese?
A．显微镜 B．探测仪 C．放大镜 D．摄像机
3．According to the passage，a pump is used to ________．
A．open or shut doors B．send something up
C．change the size of rooms D．make something in or out