题目

 —Why didn’t Betty come to school yesterday? —_________ she was ill. A．But                   B．Though            C．If              D．Because 答案：D黑皮肤往往比白皮肤不怕太阳晒，原因是（　　）A、黑皮肤黑色素含量多，吸收紫外线B、白皮肤黑色素含量多，吸收紫外线C、黑皮肤黑色素含量多，反射紫外线D、白皮肤黑色素含量多，反射紫外线