Exp) Option c is the correct answer.

Bombay Municipal Corporation (BMC) has been using the Miyawaki method to create tiny urban forests in the Metropolitan areas of Mumbai. Miyawaki is an afforestation method based on the work of Japanese botanist Akira Miyawaki in the 1980s.

Process of Miyawaki Method:

• Initially, native trees of the region are identified and divided into four layers-  shrub, sub-tree, tree, and canopy.
• After that, the quality of soil is analyzed and biomass is mixed with it. Biomass mixing help to enhance the perforation capacity, water retention capacity, and nutrients.
• A mound is built with the soil and the seeds are planted at a very high density. Furthermore, the ground is covered with a thick layer of mulch.
• Multi-layered saplings are planted close to each other. This blocks sunlight from reaching the ground and prevents weeds from growing. It also keeps the soil moist.
• The close cropping also ensures that the plants receive sunlight only from the top. It enables them to grow upwards rather than sideways.

Source:  

https://forumias.com/blog/miyawaki-method-to-create-dense-green-patches/#:~:text=Process%20of%20Miyawaki%20Method%3A&text=A%20mound%20is%20built%20with,and%20prevents%20weeds%20from%20growing.