68. The Mississippi riverboat, which evolved from simpler steamship of the early 1800’s, became the dominant form of passenger transport on the LACE w:st="on">Mississippi RiverLACE>. 答案： steamshipàsteamships

分析：单数可数名词不能单独出现。需要注意的是，transport这里作名词，有“运输工具”的意思

参考译文：密西西比河船，在1800从简单的汽船演变过来，成为密西西比河上重要的旅客交通形式。

为什么不选C， passenger transport 不应是复数形式么，且B与The Mississippi riverboat形式对成呀，谢谢le

我也不知道这个帖子为什么没有人答，难得回来，顺手就答了吧。

Transport

1
[uncountable] British English a system or method for carrying passengers or goods from one place to another

American Equivalent: transportation air/rail/road transport

*Improved rail transport is essential for business.

*commuters who travel on public transport (=buses, trains etc)

*It's easier to get to the college if you have your own transport (=a car, bicycle etc) .

means/mode/form of transport *Horses were the only means of transport.

2
[uncountable] the process or business of taking goods from one place to another
American Equivalent: transportation
transport of
Canals were used for the transport of goods.
3
[countable] a ship or aircraft for carrying soldiers or supplies
4
be in a transport of delight/joy etc
literary to be feeling very strong emotions of pleasure, happiness etc

Remember!单数可数名词不能单独出现；要么加冠词（a不定冠词/the定冠词），要么用复数。

steamship =[countable]a large ship that uses steam to produce power

The Mississippi riverboat 单数名词前有限定词the，所以可以存在。

但我第一次选transport的……现在明白了