I think that the idea behind rejecting C is that it comes close but doesn't not quite reach the desired answer level . JY mentioned the "must" part, but I also was not fully convinced. By doing a blind review, I came to the conclusion that even though the "beauty of the river crossing must be preserved (C), nothing states that building a new concrete skyway would compromise the beauty of the river. Whereas choice E, makes the distinction in that the cable bridge is better than the skyway because it is aesthetically pleasing (vague meaning for beauty).

1) FML - LMF

2) FLG - GLF