C
What is blood? It is the red liquid which comes out of your finger when you cut it. There are bout thirteen pints(品脱) of blood in a man' s body. He can give a pint of blood at a time to
blood bank for the use of other men who may need it. A healthy body makes up one pint of bloo
quickly.
What does our blood do for us? It takes food to all parts of our bodies and takes waste awa
from them. All the parts of our bodies are made up of cells, and these cells, which are very small
all need food all the time.
The blood is like a stream. The cells take what they need out of the blood stream, as plants an fishes take their food out of water. The blood stream carries food and oxygen which it has taken up our lungs to all the cells in the body.
What makes the blood go on moving round the body in a stream? The heart sends it round.
man' s heart is about the Size of his fist. The heart is a pump. It has rooms in it with doors betwee
them. It pumps blood in and out through these doors by changing the size of the rooms so that th
doors open and shut.
The heart keeps stream of blood going all round the body and back again to itself. Everywhel the blood stream does two things: supplies the cells with food and oxygen and takes away the waste It is as if the blood kept the little fires in the cells burning and took away the ashes.
49. Blood is the_____
A. red liquid which comes from your finger B. red liquid which we can see
C. red liquid which flows in a man's body D. red cell
50. The blood in a man' s body__________.
A. makes food all the time
B. takes food to all cells in the body and takes waste away
C. supplies the cells with food and oxygen from them
D. takes waste away from the cells
51. __ makes the blood go on moving round the body in a stream.
A. The heart B. The lung C. The cell D. The pump
52. This article tells us about__________.
A. a stream of blood B. the use of the heart
C. a wonderful pump D. something about blood
，所以高一学生共
人，高二学生共有
人，所以共有高三学生
，所以根据分层抽样的抽取方法可知在高三中抽取的学生人数为
