Explanation:

• Chinook winds develop when warm, moist air blows from the Pacific Ocean in the northwest region of North America toward the Rocky Mountain range, according to Rocky Mountain National Park.
• Foehn. Foehn, German Föhn, warm and dry, gusty wind that periodically descends the leeward slopes of nearly all mountains and mountain ranges. The name was first applied to a wind of this kind that occurs in the Alps, where the phenomenon was first studied.
• Therefore it is caused by strong regional winds while passing over a mountain. Hence option 1st is correct.