何时可以省略which,who,what等本来在百度里搜了这个问题,发现一位朋友的回答是：当被修饰的先行词做宾语时可以省略,而先行词是主语时则不可以省略.并举例说the teachers who were inveted to the conc

何时可以省略which,who,what等本来在百度里搜了这个问题,发现一位朋友的回答是：当被修饰的先行词做宾语时可以省略,而先行词是主语时则不可以省略.并举例说the teachers who were inveted to the conc
何时可以省略which,who,what等
本来在百度里搜了这个问题,发现一位朋友的回答是：当被修饰的先行词做宾语时可以省略,而先行词是主语时则不可以省略.并举例说the teachers who were inveted to the concert arrived on time中由于teachers是主语,因此who就不能省略.但是我有两个问题：
1.All I need is diligence.中all作为主语,不就省略了all（what） I want is diligence中的what吗?
2.在chinadaily中看到一句话：She said the twice-yearly forum,launched by the presidents of the two countries,and the successful implementation of promises made at the first two sessions reflect efforts made by the two sides to settle economic disputes through negotiations.
其中 twice-yearly forum和the successful implementation of promises应该是reflect的主语啊,但是为什么文中写the successful implementation of promises made at the first two sessions而不是the successful implementation of promises which is made at the first two sessions?
小弟水平有限,这个问题确实不懂,希望懂的朋友能帮我解答,不要一大段语法书直接粘过来让我自己找,最好详细点,

何时可以省略which,who,what等本来在百度里搜了这个问题,发现一位朋友的回答是：当被修饰的先行词做宾语时可以省略,而先行词是主语时则不可以省略.并举例说the teachers who were inveted to the conc
All I need is diligence.中并不是省略了what,而是省略了that.
英语的定语从句中,all that=what
原句应为All（that) I need is diligence.
在英语中,过去分词作后置定语表示被动.因此made表示the successful implementation of promises 的状态是被动的.