比如You can't have seen him,since I went to an international conference with him.
since前面可以加逗号吗?
答：一般不加,如有插入语,或主句较长,想歇口气,就可以加.
这个例句有误,since应改为for
since表示原因时,常放在主句的前面,译作‘既然’.