Which of the following literary techniques best describes Achebe's use of the folktale about the tortoise and the birds? irony extended metaphor direct characterization foreshadowing

The correct answer is B: extended metaphor.

This folktale is an allegory (which is an extended metaphor). While on the surface the story is about a tortoise and birds, this story can also be seen as a tale of people and their oppressors. In this case, the tortoise represents the oppressor and the birds the oppressed.