Answer:
B. a decrease net export spending caused by an appreciation of the home currency
Step-by-step explanation:
When the aggregate demand curve shifts to the left, it means that total consumer spending decreases. This decrease might result from consumers having less money due to a rise in unemployment, high inflation, a decrease in economic activity or an increase in taxes. This type of shift is specially "dangerous" for the economy because consumer spending represents almost 70% of the GDP.
In this case, the appreciation of the US dollar resulted in a decrease in economic activity of exporting companies.