920. When Congress reconvenes, some newly elected members from rural states will try and establish tighter restrictions for the amount of grain farmers are to be allowed to grow and to encourage more aggressive sales of United States farm products overseas.
(A) and establish tighter restrictions for the amount of grain farmers are to be allowed to grow and to encourage
(B) and establish tighter restrictions on the amount of grain able to be grown by farmers and encouraging
(C) establishing tighter restrictions for the amount of grain farmers are allowed to grow and to encourage
(D) to establish tighter restrictions on the amount of grain capable of being grown by farmers and encouraging
(E) to establish tighter restrictions on the amount of grain farmers will be allowed to grow and to encourage

答案是E
When Congress reconvenes, some newly elected members from rural states will try to establish tighter restrictions on the amount of grain farmers will be allowed to grow and to encourage more aggressive sales of United States farm products overseas.

will be allowed to grow 是修饰谁的，为什么用将来时，而不是一般现在时？

 那就是说，这个句子本来是将来时will， 里面的词gain又用一个将来时的句子作定语从句来修饰？

麻烦把它省略的东西补出来吧，我还是有点看不懂。