All________ made______ possible for China to succeed in carrying on its reforms and open-door policy.

 [      ]

A. what happened; it

B. what happened; that

C. that happened; it

D. that happened; that

韩红在《天路》中这样唱道：“那是一条神奇的天路哎，把人间的温暖送到边疆，从此山不再高路不再长，各族儿女欢聚一堂”。“天路”的开通[ ]

①可以彻底解决西藏的交通问题

②凝聚了我国各民族人民的心血和智慧

③有利于促进西藏地区的繁荣和发展

④有利于促进我国各民族的交流与团结

A．①②③

B．①②④

C．①③④

D．②③④