The practice of clearing forests and planting a single species of plant promotes (b) monoculture in the area.
Explanation: Monoculture refers to the cultivation of a single crop species over a large area, which drastically reduces the variety of plant life in that region, negatively impacting biodiversity.
Why the other options are incorrect:
(a) biodiversity in the area:
Monoculture significantly decreases biodiversity by eliminating most other plant species in the area.
(c) growth of natural forest:
Clearing forests for monoculture actively prevents the growth of a natural forest, as it disrupts the natural ecosystem.
(d) preserves the natural ecosystem:
Monoculture drastically alters the natural ecosystem by introducing a dominant single species, thereby destroying the existing ecological balance.