Is human blood all the same? “Yes，” you may say．“It's all red．”

Well，it's not as simple as you might think．

Blood is made up of different parts，such as red blood cells，white blood cells，and platelets（血小板）．

Two chemical molecules（分子）on the red blood cells make people's blood different．Scientists mark one molecule "A" and the other molecule "B".

According to which and how many molecules are on the red cell, scientists divide blood into four types: A, B, AB and O.

Your blood type will stay the same your whole life.

Scientists have been wondering if there are some links between people's blood type and their personalities but they don't know for sure yet.

  But some say that people with the same blood type may have things in common.

What's your blood type? Do you have family members or friends who are the same type as you? Read the following. Are you like this?

People with type A: They look peaceful from the outside. But they ask too much of themselves that they may be very nervous inside. They get happy or sad easily. Sometimes they are shy but always very careful. They can easily win people's trust.

People with type B: They have strong minds. Once they start a task, they don't give up easily. They'll try their best to finish it and do it well. Type B people always try to make themselves different from others. They want to do things in their own way in life.

People with type AB: They are maybe the strangest among all blood types. They can be both open and shy, noisy and quiet at the same time! They are responsible （負責(zé)的） and always ready to help others.

People with type O: They're open and good at making friends. They always start tasks but don't always finish them. They have lots of new ideas and love to be the centre of attention. They always strongly believe in themselves.

1. What's the main subject of this passage?

A．blood types                                      B．blood types and personalities

C．personalities                                      D．scientific research on blood

2. The blood types are decided by ____________.

A．the amount of white blood cells

B．the amount of platelets

C．the kind and amount of molecules on the red cell

D．the kind and amount of molecules on the white cell

3. Scientists are ________ about the relation between blood types and personalities.

A．not sure                    B．quite sure            C．excited               D．worried

4. If a person always tries to be different from others, he/she might have _________ blood.

A．A type               B．B type                C．AB type              D．O type

5. Which of the following is NOT true according to the passage?

A．A person's blood type will never change throughout his life.

B．A person's blood type might have something to do with his/her personality.

C．A person with type O blood is usually confident.

D．A person with type A blood has the strangest personality.