《prep语法笔记》65题，关于平行的问题

yx5271

求帮助，对PREP 中的解释不理解！
以下题目的正确选项是D,  
prep 提供的解释说 wagons had high wheels… and  a floor结构平行。
可是我不理解这种平行，我理解的平行应该为 wagons had high wheels… and  had a floor..........    
是不是D 项中的, and 后省略了 had 呢？

Developed by Pennsylvania's Palatine Germans about 1750, they made Conestoga wagons with

high wheels capable of crossing rutted roads, muddy flats, and the nonroads of the prairie and they

had a floor curved upward on either end so as to prevent cargo from shifting on steep grades.

(C) Conestoga wagons, with high wheels capable of crossing rutted roads, muddy flats, and the

nonroads of the prairie, and had a floor that was curved upward at both ends to prevent

(D) Conestoga wagons had high wheels capable of crossing rutted roads, muddy flats, and the

nonroads of the prairie, and a floor that was curved upward at both ends to prevent

(E) Conestoga wagons had high wheels capable of crossing rutted roads, muddy flats, and the

nonroads of the prairie and floors curving upward at their ends so that it prevented

anye199117

同问 = =