[单项选择]But, in the United States and in Europe, there is a growing danger that, as the attractiveness and impact of biology develops, an inadequate appreciation of physics will effectively lead to a ______ against it.
A. backwash
B. backlash
C. background
D. backing

[单项选择]But, in the United States and in Europe, there is a growing danger that, as the attractiveness and impact of biology develops, an inadequate appreciation of physics will effectively lead to a ______ against it.
A. backwash
B. backlash
C. background
D. backing

[单项选择]How many states are there in the United States
A. Thirteen.
B. Fifty.
C. Fifty one.
D. Sixty.

[单项选择]After 1850,various states in the United States began to pass compulsory school attendance laws.
A. harsh
B. diversified
C. mandatory
D. complicated

[单项选择]The United States is a confederation of states．Each state has the (26) to make laws with regard to the state． (27) , based on public opinion，states can (28) policies regarding education, and they may (29) a state income tax; they also determine the speed (30) , housing codes and the drinking age．
In most parts of the United States, you (31) be 21 years old to buy alcohol in a liquor store, bar (32) restaurant．In some states you may buy beer in a grocery store．If a store sells alcohol to a minor,the (33) of the store is usually (34) a large sum of money．
(35) many areas have an open-container law, (36) means that people may not drink alcohol on the street or in a car．Anyone (37) with an open container of alcohol may be arrested．
(38) with all these laws, the (39) of alcohol is a serious (40) in the United
A. can
B. shall
C. may
D. must