题目

已知关于x的一元二次方程(a－1)x2－2x+1=0有两个不相等的实数根,则a的取值范围是(     ) A．          B．          C．且a≠1           D． 答案：C Without proper __1________(plan), tourism can cause problems. For example, too many tourists can crowd public places __2_________ are also enjoyed by the inhabitants(居民) of a country. If tourism creates too much traffic, the inhabitants will become __3________ (annoy) and unhappy. They begin to dislike tourists __4_______ to treat them impolitely. They forget how much tourism can help the country’s economy. __5_________ is important to think about the people of a destination country and ___6________ tourism affects them. Tourism should help __7________ country keep the customs and beauty that attracts tourists. Tourism should also advance the wealth and ___8_______ (happy) of local inhabitants. Too much tourism can be a problem. If tourism __9_________ (grow) too quickly, people must leave other jobs to work __10________ the tourism industry. This means that other parts of the country’s economy can suffer.