happen to是某事发生在某人身上,sth.happen to sb.
happen on 是偶然遇见或发现,比如I happened on this old photograph in the back of the drawer.也可以说happen upon happen to是某事发生在某人身上,sth.happen to sb.
happen on 是偶然遇见或发现,比如I happened on this old photograph in the back of the drawer.也可以说happen upon