9 In arithmetic， a number stands for the size of a set of things.
A measures
B estimates
C cancels
D represents
10 Some species of bacteria and fungi thrive on simple compounds such as alcohol.
A mix with
B do well on
C exist in
D float on
11 Why do you want to throw away those books？
A imitate
B discuss
C extract
D discard
12 The Pullman Strike of 1894 tied up transportation and was finally ended only by government intervention.
A relied upon
B hindered
C linked with
D imitated
13 Although a herd of African elephants may have up to one thousand members， Asiatic elephants live in bands of five to sixty animals.
A as many as
B more than
C fewer than
D at least
14 Prohibition in the United States ushered in an era of crime and corruption.
A introduced
B caused
C used
D upset
15 The Spanish， French， Dutch， and English all vied for North American territory.
A arrived on
B competed for
C disposed of
D sailed for