Use the table to answer the question.

Days sunny and warm
1. A warm air replaced by an cold air mass
2 cloudy and rainy
3 drop in temperature
4 clear skies and cold temperatures

A student tracks the daily weather. The student’s observations are logged in the table. Which factor in the atmosphere best explains the student’s observations?

1. A warm air mass replaced a cold air mass.
2. A cold front moved into the area.
3. High levels of moisture are contained within an air mass.
4. A warm front moved into the area.

Based on the observations in the table, the best explanation for the student's observations is that a cold front moved into the area. This is suggested by the following observations: cloudy and rainy weather (2), drop in temperature (3), and clear skies and cold temperatures (4). A cold front typically brings cooler temperatures, precipitation, and clearing skies.