单选题
6. There are many structural and thematic similarities between
Piers Plowman by Langland (1330-1400) and
House of Fame by Chaucer (1342-1400), two Middle English poems relating dream visions. Some critics have argued that because a number of the shared elements are uncommon in Middle English poetry, and because Langland's poem probably predates Chaucer's by a few years, Chaucer was most likely influenced by
Piers Plowman when writing
House of Fame. Which of the following, if true, most seriously weakens the critics' argument? ______