The correct answer is D, Hope that helps! :)
Keystone species ; this is a species whose presence is critical to the composition and integrity of the community
Saturated fatty acids are chains of single bonded carbons surrounded by hydrogen atoms.
Unsaturated fatty acids have bent structures due to double bonding between carbon atoms in the chain. When carbons create double bonds with each other they are no longer able to hold as many hydrogens as a saturated fatty acid
Your answer would be A. The earth element stays in the same area of the lithosphere, hydrosphere, or atmosphere where they originated when the earth was formed.
