题目

阅读短文，回答问题When I was 16 yearsold, I made my first visit to the United States. It wasn't the first time that Ihad been abroad. Like most British children, I learned French at school and I hadoften been to France, so I was used to speaking a foreign language to people whodidn't understand English. But when I went to America, I was really looking forwardto having a nice and easy holiday without any language problems. How wrong I was! The misunderstanding began atthe airport. I was looking for a public telephone to give my friend Mary a ringand tell her that I had arrived. A fri下列命题中，真命题是（　　）A．?x∈R，x2-x-1＞0B．?α，β∈R，sin（α+β）＜sinα+sinβC．?x∈R，x2-x-1=0D．?α，β∈R，sin（α+β）=cosα+cosβ