Read the passage below and use it to answer the question. Rainforests have four basic layers. The tallest trees are part of the emergent layer, which can be as much as 60 m above the ground. The sunlight is bright and hot here, and the wind can be strong. The main layer of the rainforest is the canopy, more than 20 m above the ground. It is made up of the leaves and branches of tree tops. The air here is still and very moist. The canopy blocks out most of the sunlight. Smaller trees, vines, and other plants make up the understory, which is less than 12 m above the ground. This layer is damp and warm with very little sunlight. The forest floor is dark, warm, and moist. Decomposers break up fallen leaves and other dead matter here. Which of the following graphs best presents one of the abiotic factors of a rainforest?