Hi!
For ludacrispat26: yes, the first half of the sentence is a bit confusing but not if you recognize the speaker's intended meaning. "them" does seem, technically, to be referring to "first appearance" but obviously that can't be right. Because this is the non-underlined portion, however, we know it must be correct, and "them" must be referring to the "poems."
Most likely, this issue would not show up in an underlined portion because, there, grammatical correctness is more important than style. (For the underlined portion, you have to consider 1) grammar, 2) preservation of speaker's intended meaning, and 3) style, in that order).
"it" is the only pronoun that does not need to replace an explicit noun; instead, "it" can just refer to the state of the world.
A choice with the word "by" in it should always make you worry about style, and the word "by" shows up in a lot of wrong answers. It usually indicates the passive voice ("the ball was kicked by Billy" vs "Billy kicked the ball".)
Kaplan Teacher in Toronto