第20题: [单项选择]______pollution control measures tend to be money consuming, many industries hesitate to adopt them. A. Although B. However C. When D. Since 参考答案:D 答案解析:[解析] 在做此题时根据前后句意衔接,我们知道应该是因果关系,故答案只能为D。since在这里表示原因。although意为“虽然”;however意为“然而;when意为“当……时候”。