请教牛牛3道语法题,是大全上的

(1)    In presenting his modus Vivendi proposal, Lansing implied that the American government accepted the German view that armed merchant vessels were warships: however, when the proposal was dropped by the Wilson administration, it seemed to be reverting to the British view on this question.

A when the proposal was dropped by the Wilson administration, it

B after it was dropped, the Wilson administration

C by dropping the proposal, the Wilson administration

D the Wilson administration dropped the proposal when it

E when they dropped the proposal, the Wilson administration

我的疑问是A与C 。 C 除了主动优于被动以外，
        还有其他原因吗？

2 The work of mathematician Roger Penrose in the early 1970s, on the geometry of what are called aperiodic tiles, turned out to describe the architecture of a previously unknown class of crystals.

A what are called aperiodic tiles, turned out to describe.

B what is called aperiodic tiles, described

C apeiodic tiles, describing

D so-called aperiodic tiles, describe

E aperiodic tiles, it turned out to describe

我的疑问点在A 与B之间。
        不明白为什么是are  啊？难道是因为aperiodic tiles 啊？语法怎么分析呢？

3. In spite of continuing national trends towards increased consumption of specialty foods, agronomists in the Midwest foresee a gradual reversion to the raising of agricultural staples: feed corn and hard red wheat.

A 同上

B that a gradual reversion back will feature the raising of agricultural staples

C a gradual reversion back to the raising of agricultural staples again

D a gradual reversion to raise agricultural staples

疑问点在A和D 为什么是the raising of 而不是raise sth?不是后者更简练吗？

以上答案分别为C A A。

希望多多发表看法

1. not clear what "it" refers to

2.是因为aperiodic tiles

3. a reversion to sth., need a n. here.

啊,谢谢啊!!