This question tests three closely related words built from the same root "epi-": epigram, epitaph and epigraph. Each has a distinct, specific use, and the sentence is built so that only one arrangement of the three makes sense across all four blanks.
Reading the finished sentence confirms it: "Mark Twain was responsible for many striking, mostly cynical epigrams... Epigrams can sometimes end up as epigraphs, but rarely would someone use them as an epitaph." That flows correctly and uses each word for its real meaning.
Let's summarize:
So the sentence is completed by epigrams, Epigrams, epigraphs, epitaph, which is option 4 (originally E).