Please help! A. Why would the saguaro be considered a keystone species in its ecosystem?

B. Name examples of predation, mutualism, and commensalism that involve the saguaro.

C. What is one way a desert ecosystem would be affected if environmental changes were to cause a decrease in the saguaro population?

This is what i did 45-5=4040÷4=10so there are 10 white marbles but am not sure is just a question that am not sure

The answer is atmosphere. there are four spheres of the earth: 1. geosphere (from greek word 'geo' = ground), 2. hydrosphere (from greek word 'hydro' = water), 3. biosphere (from greek word 'bio' = life), and 4. atmosphere (from greek word 'atmo' = air). a magnetosphere is a region of space around astronomical objects controlled by the magnetic field of that object. through the process of elimination, since lightning is present in the air, it can be found in the atmosphere.