据报道，全球观看北京奥运会开幕式现场直播的观众达2 300 000 000人，创下全球直播节目收视率的最高记录．该观众人数可用科学记数法表示为______人．

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