填空题 Look at the four squares, , , , and , which indicate where the following sentence could be added to the passage. Where would the sentence best fit?
However, the ground surface is spongy and wet to the touch.
Bogs are a distinctive type of wetland. They appear relatively dry, with only small amounts of shallow water visible. The surface material is largely sphagnum moss or other organic matter rather than mineral soil. Bogs are usually characterized by evergreen trees and shrubs and are underlain by deep peat deposits.