--As we know China is still a country while the U.S.A. is a country.A.developing;develope

问题补充：

--As we know,China is still a country while the U.S.A. is a country.

A.developing;developed B.developed;developing C.developed;developing

答案：

解析：句意：正如我们所知，中国还是一个发展中的国家，而美国是一个发达国家。developing正发展着的,developed发展过了的，发达的，故选A。