The plan is heard designed so well that we don’t have to make any changes. 

参考译文：听说这个计划设计的如此之好以至于我们没有必要作任何改动。

以上为过去分词designed作主语补足语，后面接一个so+adv.+that引导结果状语从句。   

— It is indeed.

A. to design         B. designing    C. designed   D. design  

以上主句谓语部分有以下2种理解：

(1)is heard designed=is heard (to have been省略) designed 一个简化/缩写形式

备注：to have been designed表示被动的不定式动作在谓语动词之前发生。(不定式作主语补足语）

(2)is heard designed=is heard (to be省略) designed 一个简化/缩写形式

备注：to be designed表示被动不定式动作在谓语动词之后/同时发生。（不定式作主语补足语）

如果用不定式也可以，那就是：to have been desinged。即：

The plan is heard to have been desinged so well that we don’t have to make any changes.  听说计划做得很好，我们不需要做任何修改。

—The plan is heard _____ so well that we don’t have to make any changes.     

— It is indeed.

A. to design         B. designing      C. designed         D. design     

这题选 C，但是 sb is heard to do sth 被动要把 to 添加上，可是主语是sth为什么就不适用了呢？

   【答】根据句意，这里的 is heard 的意思应该是“（被）听说”，而不是“（被）听见”。

    当hear作“听说”解时，通常使用 hear that 或者 hear it said that 句型，其中的 that 也可以省略；没有sb is heard to do 或 sth is heard （to have） been 这样的用法。例如：

    I was surprised to hear (that) he was married. 听说他结婚了，我很惊奇。（《牛津高阶英汉双解词典》第九版 hear）

    I hear you've been away this weekend. 我听说你这个周末外出了。（同上）

    I've heard it said (that) they met in Italy. 我听说他们是在意大利认识的。（同上）

    所以，网友的句子没有正确答案，句子结构错误。前一个句子可以改为：

    I hear (it said) that the plan has been designed so well that...

    或者

    The plan is said to have been _____ so well that... (答案是 C)