Air masses are huge expanses of air that form from differential heating in the atmosphere. The boundary between two air masses is called a weather front. Fronts can create particular types of weather. Identify each front by the weather it produces.
warm
stationary
cold
occluded
A cold air mass advances on a warm air mass, causing rain.
A warm air mass advances on a cold air mass, causing rain.
Air masses that are close in temperature collide, typically leading to mild weather.
Three air masses meet, usually leading to strong winds and heavy rain.

Explanation: An air mass can be define as the body of air whose properties such as humidity, temperature and other features are homogeneous. The air mass can vary according to the location. The warm front is formed the warm air mas replaces the cold air mass.The cold front is formed when a cold air mass replaces a warm air mass. The stationary front can be define as a weather condition in which the cold and hot air masses lie in opposite directions and neither of them are capable of displacing each other. As, a result of this a static weather condition develops. In stationary front the weather remains mild. In occluded front is formed when a cold air mass overtakes a warm air mass and goes underneath it.  

On the basis of the above description, the following are the matches:

A.) warm  2.) A warm air mass advances on a cold air mass, causing rain.

B.) stationary  3.) Air masses that are close in temperature collide, typically leading to mild weather.

C.) cold 1.) A cold air mass advances on a warm air mass, causing rain.

D.) occluded  4.) Three air masses meet, usually leading to strong winds and heavy rain.