IMO - CEliminate A, and D, because Thomas Edison cannot represents a person, and person cannot be compared with age.
Remaining with B, C and E
Phrase what many of us thought/think clearly modify the age of American innovation
But what makes reject B, and E
in Option C, Correct Option
Dashes save the day when other punctuation would be awkward.
For instance, "dashes" can replace parentheses at the end of a sentence or when multiple commas appear in a parenthetical phrase.
And "think" usage of present tense.
Option B, is
wrong due to usage of time indicator "When" followed by comma, it compares new idea with golden age.
Option E, usage of (,in which) with preposition "in" and "which" relative pronoun as a precise way to introduce a relative clause after a noun that refers to a place or to a time, and word "thaught" past tense, but here , it means
the definition of Golden age of American innovation, which clearly usage of "Dash" makes the intended meaning correct, this makes
option E wrong