Why did poseidon think gifting humans a horse would be the most beneficial gift for humankind?

Explanation:

Poseidon, Lord of the Seas,Poseidon was most notably the God of the sea and the protector of all waters; sailors relied upon him for safe passage. Poseidon was allotted his dominion after the fall of the Titans. Zeus and Hades were his brothers. I think because he was rich

the sentence that avoid faulty coordination is:

culture, which is well represented in philadelphia, plays a major role including theatre, music, and the visual arts.  

faulty coordination occurs when the writer gives equal importance two different ideas (clauses) which in fact are not equivalent. in order to correct a misplaced clause or idea, the writer can place less important or emphatic ideas in a relative clause as in the previous sentence.