单选题 .  ①The poet Paul Lawrence Dunbar (1872-1906) was the premier Black writer of poetry that used the dialect of rural African American of the southern United States. ②Although Dunbar's works were both popular with readers and acclaimed by literary critics during his lifetime, after the First World War a radical shift occurred, at least in critical opinion of his poetry, and twentieth-century critical evaluation of his work has been generally negative. ③Some critics attacked his work on social grounds for failing to challenge plantation stereotypes of African Americans. ④Other critics, such as the post James Weldon Johnson, argued from aesthetic grounds that dialect poetry in general was too limited as an artistic medium, and capable of producing only two effects: pathos and humor. ⑤The negative critical trend only began to reverse itself in the 1970s, when scholars began to emphasize the importance of mythic, psychological, and historical dimensions of Dunbar's works, focusing on the interior and exterior realities of African American life after the Civil War.41.  Which of the following general criticisms of dialect poetry is mentioned in the passage? ______