Sometimes the A(horses) are caused by A (horses), but at other times—when, for example, because of the distance or conditions of low visibility, one has confused a cow for a horse—the A (horses) are caused by B (cows).
有时候A（马）是由A（马）所导致的，但在其他时候——例如，当由于距离远或能见度低的情况，一个人把牛混同为马时——A（马）是由B（牛）所导致的。