Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks. 

Part of what makes summers so hot is also what causes thunderstorms. As heat from the sun beats down on Earth, the heat evaporates some of the water in lakes and oceans. The evaporated water stays in the air. This evaporated water makes the air feel heavy and humid. Humid air is what makes you feel hot and sticky (1) _______ the summer. 

Warm humid air usually does not stay in one place. The wind can move it higher in the sky (2) _______ it will cool off. When warm humid air cools, it forms clouds. As more water is moved from lakes and oceans to the airs, the clouds get bigger and bigger. 

Since summer, the air near the ground is hotter than it is during other seasons of the year. When this hot air mixes with cool air from (3) _______ area, there will be changes in the weather. Greater differences between the (4) _______ of the hot and cold air will cause greater changes in the weather. Imagine putting an ice (5) _______ in a warm drink. As soon as the ice hits the warm drink, it will crack and pop. But if you put the ice cube in a cool drink, it will not crack or pop as much. When warmer and cooler clouds get close to one another, there may be some popping and cracking as the weather changes. There may be more clouds or storms. A thunderstorm may be on its way.