省略应该是 at speeds (that are) much higher than (speeds) are currently possible这样才平行
D. at much higher speeds than that
E. at speeds much higher than are DE的的比较对象不同,楼主仔细体会一下,如果用D的形式,那应该是at much higher speeds than at ......;而E只是对形容词high的比较。
-- by 会员 三脚猫 (2005/10/23 17:37:00)
不明白D补全为什么就是at much higher speeds than at...呢?第二个at不能省略吗?补全后不可以是at much higher speeds than the speeds currently possible吗?然后用that代替第二个speeds。D应该是that不能指代复数的speeds,所以错了吧?