答案C
research into对...研究:1)(作动词用)He is researching into the reading problems of young school children.2)(作名词用)to carry out a research(="some" research)into the causes of brain damage.(对大脑损伤原因进行研究).
研究可译为make researches into,make a study of 或直接用动词study vt或research into (a problem etc.).
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