中国問題SC 2問

中国問題SC 2問です。

1.Most nations regard their airspace （as extending） upward as high as an aircraft can fly; no specific altitude, however, has been officially recognized as a boundary.

A. as extending
B. as the extent

Aが正解ですが、extending upwardの文構造を教えて下さい。
upwardは副詞、extendingは動名詞でしょうか？
regard asのas以降はこの問題のように動名詞を取ることがあるのでしょうか？

2.When congress reconvenes, some newly elected members from rural states will try （and establish tighter restriction for the amount of grain farmers are to be allowed to grow and to encourage） more aggressive sales of United States farm produces overseas.

C. establishing tighter restriction for the amount of grain farmers are allowed to grow and to encourage

E. to establish tighter restriction on the amount of grain farmers will be allowed to grow and to encourage

Eが正解ですが、Cはどこが駄目でしょうか？try to establishとtry establishingはこの場合、同じ意味に取れるのですが。

宜しくお願いします。