What are two factors that can increase the national debt?

As you probably know, when Bill Clinton left office, the budget was in surplus and both the White House and the Congressional Budget Office projected that the external U.S. debt would be completely repaid by about 2010. Instead, we're more than $12 trillion dollars worse off.

i believe the correct answer is option b. most eastern european nations joined nato.

though i could be wrong, option d. the eastern european nations were granted complete independence, would be another choice.

hope this ! : )