pen是可数还是不可数名词

　　Go and get me a pen please.

　　请你去给我拿支钢笔来。

　　I could hear his pen scraping across the paper.

　　我听得见他的'钢笔在纸上沙沙地响。

　　At the stroke of a pen they removed thousands of people from the welfare system.

　　他们大笔一挥，就把成千上万的人排除在福利制度之外。

　　None of these pens works/ work.

　　这些钢笔没有一支能用。

　　She reached inside her bag for a pen.

　　她把手伸到包里掏钢笔。