🔍 Key Concepts

• Frontal activity occurs where two different air masses meet • Differences in temperature and moisture content create instability and lift • A front is the boundary between air masses with contrasting properties

💭 Think About

• Ask yourself: What has to be true about two air masses for a clear boundary (front) to form between them? • Which choice describes conditions that would create rising air, clouds, and possible storms where the two air masses meet? • Which options would make the air masses too similar for a well‑defined front to exist?

✅ Before You Answer

• Verify which option involves significant differences in temperature and/or moisture between the air masses • Eliminate any choice where the air masses are described as having no significant differences • Consider whether same pressure and temperature would create a strong or weak boundary between the air masses