families proudly said that they had "blue blood"．But then why "blue" blood? Because they were fairskinned, and it is only natural that their blood vessels（血管）stood out appearing blue．

21．The two meanings of the term "redcap" form a difference in _______．

A．pronunciation B．climate

C．logical relationship D．custom

22．Both Britain and America would probably agree that _______．

A．black is the color of mourning

B．a black-coated worker is employed in an office

C．red stands for beauty and excellence

D．a redcap is a porter in a station

23．The best title for this passage is _______．

A．The Origin of Blue Blood

B．The Development of the Symbolic Use of Colors

C．Colors that Carry Bad Meanings

D．The Meaning Concerned With Certain Colors

24．When some Spanish called themselves "blueblood", they actually meant _______．

A．they had heart trouble and their faces looked blue

B．they came from a noble family

C．they had blue blood in their vessels

D．they were fairskinned

San Francisco is going to do what many other cities have already done-provide free bicycles for the public . The mayor of San Francisco supports the bicycle program . He wants to improve the terrible traffic problems in the city .

At first , 40 to 60 bikes will be available only to city workers . People will give their old bikes to the city to use in the program . If this program is successful , one day more than 1000 bicycles will be available . Everyone , not just city workers , will be able to use these bicycles .