Roberto lives inland in North America. He measured the temperature and precipitation every day for one winter month and calculated the average temperature and precipitation amount for each week. He recorded his results in a chart. Week Temperature Precipitation
1 0 degrees C 0 cm
2 4 degrees C 0 cm
3 7 degrees C 0 cm
4 15 degrees C 5.00 cm

Based on the chart, what type of air mass was mostly likely over his area?
A. maritime tropical
B. continental tropical
C. maritime polar
D. continental polar