Warm, dry air masses are typically formed over land in tropical areas. In these regions, the sun heats the land, causing the air above it to warm up. Since there is often little moisture available in these areas, the air mass that develops is both warm and dry.
The other options generally produce different types of air masses:
- Over water in tropical zones typically leads to warm, moist air masses.
- Over land in polar regions usually results in cold air masses that may be dry.
- Over water in polar regions tends to form cold, moist air masses.
Thus, the correct context for warm, dry air mass formation is over land in tropical areas.