Answer: decrease which shifts aggregate demand left
Explanation:
Net exports is calculated when the value of a nation's total imports is deducted from the value of the nation's total exports.
When the dollar appreciates, perhaps because of speculation or government policy, then U.S. net exports decrease which shifts aggregate demand left. This is because due to the appreciation, goods that are made in other countries, that's the import will become cheaper and import rises while export reduces.
