Which layer of the earth is suitable for growing plants?

The correct choice is "Soil" because soil is a crucial layer that provides the necessary nutrients, water, and support for plant growth. It is a complex mixture of organic matter, minerals, air, and water, which together create an environment that is conducive to plant roots. Soil composition varies widely, influencing both the types of vegetation that can grow and the overall health of ecosystems.

While the crust, which is the outermost layer of the Earth, does contain soil, it is not in itself suitable for plant growth since it is made up of rocks and minerals without the specific blend needed for sustaining plants. The mantle and core, being significantly deeper and composed primarily of molten and solid rock, are not at all suitable for plant life. Thus, soil is the correct answer because it is specifically designed to support agricultural and ecological systems.