The companies are working together to create they hope will be the best means of transpo

问题补充：

The companies are working together to create they hope will be the best means of transport in the 21st century.

A. which

B. that

C. what

D. who

答案：

A. which

B. that

(答案→)C. what

D. who

解析：C 考察名词性从句。此处缺少宾语从句的连接词，而从句 they hope will be the best means of transport in the 21st century中they hope是插入语，因此缺少主语，所以起双重作为what。