Answer:
Hard engineering options tend to be expensive, short-term options. They may also have a high impact on the landscape or environment and be unsustainable.
Explanation:
The correct answer is A) Trade winds.
Since the air balloon is just south of the Equator and it moves towards west, that means the trade winds are moving it in that direction. The trade winds are winds that are active around the Equator and there direction of movement is east-west, thus they are wind that blows to the west.
Waning Gibbous.
Dunno why it's called that to be honest. just read into the topic