...create what they hope will be the best means of transport in the 21st century这是嵌入式名词性关系分句,作create的宾语。what=the thing which。即：...create the thing which they hope will be the best means of transport in the 21st century这样，就是名词the thing作create的宾语，后接限制性定语从句。而这个定语从句为“嵌入式定语从句”，即定语从句本身又是个主从复合句，关系代词在定语从句的从句中作成分。本句中，which是定语从句 they hope的宾语从句的主语，which的谓语为will be...关于嵌入式定语从句，网友可以参读：http://ask.yygrammar.com/q-28383.html