单选题 ______ pollution control measures tend to be money consuming, many industries hesitate to adopt them.
A. Although B. However C. When D. Since

【正确答案】 D
【答案解析】本题测试连词的用法。根据前后句意衔接，应该是因果关系，故答案只能为D，Since在这里表示原因。Although虽然：However然而；When当……时候。