题目

—Is using a mobile phone harmful to people’s health? —Scientists ________ this problem,  and no exact conclusion has been drawn yet. A. have studied                                         B. were studyingC. have been studying                                D. had been studying 答案：【解析】选D。考查as. . . as. . . 结构。句意为：到目前为止他们拥有的设备与我们拥有的一样多。equipment是不可数名词，不能用many修饰，所以可排除A、C两项。根据句意可知正确选项为D。

查看本题答案和解析