Answer to Question 1
For most countries it measures international reserve changes. For the United States, it records changes in short-term U.S. liabilities held by foreign monetary agencies. This demand for dollar denominated short-term debt by foreign central banks permits the United States to finance current account deficits largely with dollars. Other countries must finance such deficits by selling foreign currency and, as a result, face a greater constraint on their ability to run deficits as they eventually run out of international reserves. Such a constraint does not exist for the United States.
Answer to Question 2
A