In which layer of the Earth do we live?

The correct answer is the crust because it is the outermost layer of the Earth, where all terrestrial life exists. The crust consists of solid rock, including both continental landmasses and ocean floors, and is relatively thin compared to the underlying layers. It is where we find the soil, mountains, oceans, and various ecosystems that support life.

The core is located at the center of the Earth and consists primarily of iron and nickel; it is divided into the inner core, which is solid, and the outer core, which is liquid. Neither of these layers supports life nor provides the environment necessary for living organisms.

The mantle lies between the crust and the core. While the lower mantle is primarily composed of silicate minerals and behaves like a solid over long periods, it is not where we reside. The outer mantle, specifically, refers to the upper portion of the mantle that is still beneath the crust, but it also does not provide the conditions necessary for life, as it is characterized by high temperatures and intense pressure.

Thus, the crust is the layer where all human activities take place, making it the appropriate answer.