—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 studying
C. have been studying D. had been studying
—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 studying
C. have been studying D. had been studying
【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。