Detailed Instructions: In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Q: Passage: Two kinds of wet prairies thrive in the Everglades: marl and water-marsh community. Wet prairies are slightly elevated like sawgrass marshes, but contain abundant plant diversity.  Marl prairies are located where marl covers limestone that may protrude as pinnacles or erode into solution holes: depressions formed by the same processes that create sinkholes. Solution holes, however, do not meet the water table; they are filled with rain water. The surface is covered only three to seven months of the year, but the water is usually just 4 inches (10 cm) deep. Marl is created by layers of periphyton loosely attached to the limestone, and forms a grey or white crumbly mud when it dries. When flooded, the marl can support a variety of water plants, and dwarf cypresses may grow for hundreds of years though not exceed 10 feet (3.0 m) in height. Solution holes may remain flooded even when the prairies are dry, and they support aquatic invertebrates such as crayfish and snails, as well as larval amphibians which feed young wading birds. Where the predominant soil is peat, a water-marsh community exists. Its hydroperiod is longer than the marl prairie, although its plants are less diverse. These regions tend to be on the border between sloughs and sawgrass marshes.
Alligators have created an ecological niche in wet prairies; they dig at low spots with their claws and snouts and create ponds free of vegetation that remain submerged throughout the dry season. Alligator holes are integral to the survival of aquatic invertebrates, turtles, fish, small mammals, and birds during extended drought periods. Alligators feed upon animals that visit the hole.
A:
What prairies' surface is covered only three to seven months of the year?