Question

As westerly winds blow over a north-south oriented mountain range, the airflow is deflected in such a way that a trough forms on the ____ side of the mountain

Answer 1

The correct answer is - east.
When the westerly winds flow into a north-south mountain range they will hit the west side of the mountain range, since they are a wind that comes from the west and moves to the east, while the east side of the mountain will get a downward wind on it's slops, that'll be dry and also much weaker and less intense.