Excited electrons are those which temporarily occupy a state higher than their ground state
The electron is excited if it is given extra energy, such as when a photon, or packet of light, absorbs it or if it collides with an atom.
I am sure that the answer is A.) Hierarchical Classifications. I hope that I'm right because this will affect you instead of me! But just in case, check this website. It says that a major contribution was Hierarchical Classifications before Binomial Nomenclature.
http://education-portal.com/academy/lesson/carolus-linnaeus-classification-taxonomy-contributions-to-biology.html
(copy and paste)
A quick Google search revealed that Andrew Johnson was the 17th president of the United States.
This is a symbiotic relationship, where both the partners, fungi, and plants are mutually benefitted by exchange of nutrients and none of them is being harmed by other's presence. It is a mutual cooperation and helps both organisms in survival and nutrition.
