You can expect frontal activity when two air masses collide and __________.

Correct Answer: Option B — there are significant differences between the temperature of each air mass

Frontal activity is the transition zone between air masses of different densities, primarily driven by temperature contrasts. When these masses collide, the warmer air is forced upward, leading to cloud formation and precipitation. Significant temperature differences are the fundamental requirement for the development of active weather fronts in meteorology.