We know _____America is great not because it is perfect but because it can always be made better and _____ the unfinished work of perfecting the union falls to each of its citizens.

A．不填；不填

B．that ; that

C．that ; 不填

D．不填；which

有关资料显示，我国对外投资出现了强劲增长的势头。我国对外投资的增长表明（）

①我国已由资本输入国变为资本输出国

②我国企业的国际竞争力增强

③我国的跨国公司遍布全球

④我国的对外开放水平不断提高

A.①②

B.②③

C.①④

D.②④