One reason tundra plants are small and grow close to the ground is that a.)animals eat them before they can grow b.)water is easier to obtain at ground level c.)mosquitoes and black flies destroy taller plants d.)permafrost prevents penetration of deep roots

The answer to this question would be D.) Permafrost prevents penetration of deep roots.

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d.)permafrost prevents penetration of deep roots

Explanation:

Many aspects of the tundra make it difficult for plants to grow to a large size, to a large extent this has to do with the characteristics of the salary, such as its low temperature and hardness. This soil is called permafrost.

Permafrost is formed when plants die and organic matter accumulates. Over time, matter compacts and freezes but never decomposes. All the remains of plants that died centuries ago accumulate and store as permafrost.

The top of the mixture of soil, gravel and other fine materials is frozen for most of the year because temperatures do not increase enough to cause defrosting. But during the hot summer, the soil can thaw to a depth of 13 feet. This gives plants the opportunity to grow. However, the growing season is short and ends once the soil freezes again.

looks like the answer is     c     to me!