The two ways Geoffrey Chaucer's "The Pardoner's Tale" is filled with irony are B. Words have unexpected dual meanings. and E. The reader knows things that at least one character does not.
As a figurative expression, the irony is used literally to show the opposite of what is actually expressed. It can also be used when the reader knows more than the character.
"The Pardoner's Tale" is not filled with irony because of its moral message. It is not filled with irony because death is personified. It is not an attempt by the author to poke fun at human weakness.
Thus, "The Pardoner's Tale" is filled with irony because words have dual meanings and the character may not know something revealed to the reader.