Have you considered the company' s advice that you improve your work plan.  

A. improving your work plan..

错误原因：现在分词作定语修饰名词，表示动作已经发生的动作，且advice无法具有动作执行能力。 

B. for you to improve your work plan..

正确：动词不定式复合结构作定语，修饰名词“advice”。

C that you improve your work plan.

正确：that引导同位语从句，作前面名词“the company's advice”

下面几个句子都是正确的

(1)Have you considered the company' s advice that you improve your work plan. （同位语从句）

(2)Have you considered the company' s advice that you use to improve your work plan.（定语从句） 

(3)Have you considered the company' s advice for you to improve your work plan. （不定式复合结构作定语）