lawyers and businesspeople have to have abasic understanding of legal systems other than their own(1).The consequence of failing to DO（3） so cannot be more forcefully stated than by quoting from a recent opinion of Philippine Supreme Court Justice Cruz(2):1. their own指这个些自己所处的法律体系，后面省略了legal systems2. Cruz是一个人的姓，Supreme Court Justice，高级法院大法官3. 这里应该漏了一个docannot be more forcefully stated = is mostly forcefully stated翻译：律师和商人必须对其自身所处的法律体系以外的法律体系（译者注：即别国的法律体系）有一个基本的了解。未能做到这一点的后果，引用菲律宾高级法院大法官Cruz最近的一个观点来说明是再有力不过的了。
回答the old man has two sons,both of (whom)are lawyers.这是非限制性定语从句，whom指的是那个the man..另外，介词后只能用which/ whom.指人用whom指物用which....The old man has two sons.Both of（them）are lawyers,,句中的them指的是the man的儿子，，指代的人不一样，所以用的代词就不同
