It 是形式主语，实际主语是 that those who make up the society should be prevented from communicating with each other.

　　句中有三个 who 引导定语从句修饰 those

　　全句大意为“这是那些建立种族隔离社会的人，并且希望这种社会永远维持下去的人的意图，他们企图禁止构成这个社会的人相互交流。”

　　12.Black and white must be cut off from each other， must be unable to communicate. （para.11）

　　be cut off 被隔绝

　　13.It is on this spanision that apartheid rests. （para.11）

　　to rest on /upon 意思是“建立在…之上，依靠”

　　本句是强调句，被强调部分是介词短语。译为：“种族隔离正是建立在这种分隔之上。”

　　But the real damage is in daily human relations. I have seen white children standing in one of the mixed buses rather than sit beside anyone who was not white and this seems to me so complete a rejection of another human person that it goes much further than the spanision and separation backed by law. ⒁From this kind of rejection comes a complete lack of any feeling of common humanity； ⒂the suffering of a human being ceases to be real because he has ceased to be a real human being.

　　14.…this seems to me so complete a rejection of another human person that it goes much further than the spanision and separation backed by law.（ para. 12）

　　本句是一个带有结果状语从句的主从复合句，状语从句中又包含一个比较级结构，

　　much further than … ， 代词 it 指的是 rejection “排斥”

　　backed by law 是过去分词短语作定语

　　全句大意为：“ 这在我看来是对另一个人的彻底排斥，这种排斥如此彻底，以至于超出了由法律支持的隔绝和分离。”

　　15.From this kind of rejection comes a complete lack of any feeling of common humanity.（para.12）

　　这是一个全部倒装句，谓语动词comes提到主语之前，倒装原因是主语a complete lack of any feeling of common humanity 过长。同时也为了更好地承接前文，前边刚提到rejection

　　译为：“这种排斥导致普通人性感情的彻底丧失。”

　　This is the situation， which has been created in South Africa today. The tensions are real， the threat of a violent eruption constant. And this must not be thought of simply as the product of political factors of arguments. It is a simple truth that human relations between people have deteriorated so far that dialogue， understanding ， friendship - all these are impossible.⒃

　　This is the effect of apartheid in terms of society - this is its all pervasive extent： it breeds ，if it breeds anything ， hostility： often the result is simply the bitter sterility which will bring about violence.

　　16.It is a simple truth that human relations between people have deteriorated so far that dialogue， understanding， friendship all these are impossible. （ para. 13 ）

　　本句 it 是形式主语， that 引导主语从句，其中有一个so… that 结构。

　　全句大意为：“这是一个简单的事实：人们之间的关系恶化到了如此地步，以至于人们之间的对话、理解、友谊，所有这些都成了不可能的事。”

　　补充语法知识：

　　动名词的逻辑主语

　　1.动名词前面可以加上物主代词或名词所有格，表示行为的主体，成为动名词的逻辑主语

　　例如：

　　① What‘s the use of my doing that ？

　　② I dislike John‘s coming to see me so often .

　　③ This young man somehow slipped a watch into his pocket without the teacher‘s knowing it.

　　2.在非正式英语中，尤其是当动名词在句中作宾语时，也可以用人称代词的宾格或普通格的名词修饰动名词

　　例如：

　　① Nothing can stop me trying again.

　　② Do you mind John driving you home ？