Concept:Breathing roots, called pneumatophores, help plants obtain oxygen in waterlogged soil with poor aeration.Explanation:Saltwater swamps, especially mangrove swamps, have muddy and waterlogged soil that contains very little oxygen.Mangrove plants develop special upward-growing breathing roots to absorb oxygen for respiration.These roots are not characteristic of tropical grassland, temperate grassland, or tropical rain forest.Answer:C. saltwater swamp