Which historical example clearly shows the environmental loss of commercial forestry?

Correct answer: Replacing mixed natural forests with controlled single species plantations

Direct answer: Option A, replacing mixed natural forests with controlled single-species plantations. Commercial forestry aimed to produce timber and other forest products in a planned, profitable way. Natural forests usually contain many kinds of trees, plants, animals and organisms. When such a mixed forest is cleared and replaced by a plantation containing mainly one selected species, biological diversity is reduced and the ecosystem becomes less varied. The reasoning is: commercial goal leads to selection of useful trees; useful trees are planted in an organized single-species plantation; mixed natural habitats disappear or shrink; therefore environmental diversity and ecological balance can suffer. Option A is correct because it gives the actual kind of change that shows environmental loss. Option B, starting training at Dehradun, concerns the education or training of forest officials; it does not itself show the loss of species or habitats. Option C, establishing the Forest Service, is an administrative development, not a direct environmental example. Option D, making laws written, describes a legal or bureaucratic change and does not by itself prove ecological damage. A useful exam cue is: commercial forestry often prefers uniform, profitable trees, whereas natural forests are diverse.