Here's why:

* Biosphere: This is the zone of life on Earth. It encompasses all living organisms, including plants, animals, fungi, bacteria, and even microscopic life. The biosphere extends from the deepest parts of the ocean to the highest mountain peaks, and it includes the lower atmosphere.

* Crust: This is the outermost layer of Earth, consisting of solid rock. While life exists on the surface of the crust, it does not extend into the crust itself.

* Lower atmosphere: This is the part of the atmosphere closest to Earth's surface, where most weather occurs. It is home to many living organisms, including birds, insects, and bacteria.

Therefore, the biosphere is the only option that encompasses both the Earth's crust and the lower atmosphere.