鸟类的皮肤外面有由真皮所衍生的角质物，如羽毛、角质喙、爪和鳞片等。（）
参考答案：错
解析：
将“真皮”改为“表皮”。
Salomon & Co (Lesotho) Ltd is a small company consisting of Salomon, his sons and his brother. Salomon is the managing director and a principal shareholder. Their sole business is to manufacture shoes and boots. Their principal customer takes about 60% of their sales. Due to economic recession, their principal customer decided to switch their order to a cheaper supplier. As a result, Salomon & Co (Lesotho) Ltd are now teetering on the brink of insolvency. The creditors are threatening to put the company into liquidation.Required:Advise Salomon. (10 marks)
掘进机截割头要每（）更换磨损的齿座。
A、1个月
B、2个月
C、3个月
