to"专心于"，符合句意。absorb"使全神贯注"； interest"使......感兴趣"； appeal"吸引"。

　　4．Several causes contribute to the food price hikes, such as the ________ weather and record oil paces.

　　A．abnormal B．typical

　　C．terminal D．optional

　　解析：选A　句意：好几个因素导致了食品价格的攀升，例如反常的天气和创纪录的油价涨幅。abnormal"异常的"； typical"典型的，有代表性的，一贯的"； terminal"晚期的，不治的"； optional"可选择的"。

　　5．Despite their lack of interest, Fleming kept trying out the chemical to make sure it would be safe and ________.

　　A．expensive B．complex

　　C．effective D．comfortable

　　解析：选C　句意：尽管他们缺乏兴趣，弗莱明还是继续试验那种化学品以确保它安全而有效。effective"有效的"，符合句意。

　　6．Speaking in an inspection in Yunnan Province, Xi Jinping said authorities must ________ poverty removal efforts to support the building of a rich and successful country.

　　A．anticipate B．allocate

　　C．appreciate D．accelerate

　　解析：选D　句意：习近平在云南省的一次视察讲话中说，当地政府必须加速(accelerate)消除贫困的努力来支持一个富裕和成功的国家的建设。anticipate"预期，预料"； allocate"分配，分发"； appreciate"欣赏，感激，理解"； accelerate"加速，加快，促进"。

　　7．This new engine must be thoroughly ________ before being put on the market.

　　A．made out B．picked out

　　C．tried out D．cut out

　　解析：选C　句意：这种新式发动机在投放市场之前一定要进行全面的试验。A项"辨别；理解"；B项"挑选出"；C项"测试，试验"；D项"删除，剪下"。根据语境可知C项正确。

8．The US federal government has released 252 ________ so far, covering fields including