Many people are disturbed by the genetic diversity of cancers — an inevitable consequence of random evolution. Cancer therapies【

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问题    Many people are disturbed by the genetic diversity of cancers — an inevitable consequence of random evolution. Cancer therapies【C1】______be applied fairly randomly or carelessly, but nowadays many believe that effective therapies need to be【C2】______and tailored to genetic faults in each individual’s cancer.
   However, a personalized treatment disregards the most fundamental reason why it is difficult to cure cancers【C3】______: cancer cells adapt and evolve【C4】______treatment. Even drugs that are initially effective often have a【C5】______diminishing effect, as the biological systems blocked by the treatment spontaneously compensate【C6】______re-routing the cancer cells’ internal wiring,【C7】______the cancer’s ability to spread. To use an【C8】______, traffic hot spots in towns can cause major traffic jams, but smart drivers will quickly find other short cuts. Then, in the absence of "short cuts", evolution【C9】______: naturally arising mutant cancer cells that are【C10】______the targeted drug rapidly outgrow their disabled siblings and cancer comes back.
【C1】

选项 A、had better
B、would rather
C、used to
D、were to

答案C

解析 如果癌症的治疗方案很随意、粗心,效果肯定差,所以不宜选择had better或would rather,而且这两个词组的主语通常是有生命的。同学们比较熟悉be to do…的用法,但也很少用。…was(were)to do…不单纯是be to do…的过去时,有时还有另外一个意义,表示“后来的结果”,如…an event in the 1930s that was to change the world。根据后面句子的含义,不宜选择were to,与nowadays矛盾,而used to表示“过去是……”,与nowadays形成对比。
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