chance的前的介词

chance前的介词用by，例如：

1、Several years after they'd split up they met again by chance in Paris.他们分手几年以后在巴黎又偶然相遇。

2、I saw the letter purely by chance.我看见这封信纯属偶然。

3、I met her by chance at the airport.我碰巧在机场遇见她。