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Why is the answer (a) and not ©?
My guess is that the higher appreciation would cause net exports to decrease (foreign goods become cheaper, therefore higher imports and lesser exports due to cheaper domestic goods), therefore decreasing real GDP (hence AD shifting left). Real GDP = C + I + G + (X-M).
The higher income tax would decrease demand due to decreased incomes of foreign workers, so they would consume less, thus resulting in a leftward shift of the AD curve as well.
Even if you were to say that the government would spend all the tax money it collects, the net effect would still be a leftward shift due to the decrease in net exports.