Question ATPL - Airline Transport Pilot license - Meteorology

Which of the following statements is true with regard to mountain waves? - ATPL

Mountain waves are not experienced beyond 100 miles downwind from initiating high ground, regardless of the height of the ground

The absence of cloud over high ground indicates the absence of mountain waves

Flight with headwind toward high ground is likely to be more hazardous than flight with tailwind toward high ground

Flight with tailwind toward high ground is likely to be more hazardous than flight with headwind toward high ground