3. Why does NK threaten Japan, SK and the US?

A North Korean state agency threatened on Thursday to use nuclear weapons to "sink" Japan and reduce the United States to "ashes and darkness" for supporting a U.N. Security Council resolution and sanctions over its latest nuclear test.

The Korea Asia-Pacific Peace Committee, which handles the North's external ties and propaganda, also called for the breakup of the Security Council, which it called "a tool of evil" made up of "money-bribed" countries that move at the order of the United States.

"The four islands of the archipelago should be sunken into the sea by the nuclear bomb of Juche. Japan is no longer needed to exist near us," the committee said in a statement carried by the North's official KCNA news agency.

do you have a list of sources to choose from?

the answer should be a. the sui empire, the tang empire extended from korea in the west to manchuria in the east.