Explanation:

Urban forests are created through Miyawaki, an afforestation method based on the work of Japanese botanist Akira Miyawaki in the 1980s. The technique compresses layers of a forest – shrubs, trees, canopies – on small plots of land, turning them into tiny forests. In the Miyawaki technique, various native species of plants are planted close to each other so that the greens receive sunlight only from the top and grow upwards than sideways. As a result, the plantation becomes approximately 30 times denser, grows 10 times faster and becomes maintenance-free after a span of 3 years.

Hence option (c) is the correct answer.