— Sure, it ________ the only thing on the news for the last three days.
A:would be
B:is
C:has been
D:will be
黄河流域第一个国家建立的时间是( )
—Are all the students from in your class?
—No, there are only three in our class. The others are from other countries.
我国古代官方文书的主要通信方式是( )。