OG136. Although schistosomiasis is not often fatal, it is so debilitating that it has become an economic drain on many developing countries. (A)it is so debilitating that it has become an economic (C)so debilitating is it as to become an economic
OG看不明白。C为什么不对?这里是单一主谓结构,可以用it is so debilitating as to become an economic 这样的结构,C项是不是将其倒装了?如果是这样,C项岂不比A更简洁?
补262. Sunspots, vortices of gas associated with strong electro-magnetic activity, are visible as dark spots on the surface of the Sun but have never been sighted on the Sun’s poles or equator. (A) are visible as dark spots on the surface of the Sun but have never been sighted on (B) are visible as dark spots that never have been sighted on the surface of the (C) appear on the surface of the Sun as dark spots although never sighted at (D) appear as dark spots on the surface of the Sun, although never having been sighted at (E) appear as dark spots on the Sun’s surface, which have never been sighted on