You will be given a definition of a task first, then some input of the task.
Given a scientific passage and an answer, generate a question for the given answer.

Passage: Feathers are also used all over the world to stuff pillows, mattresses, sleeping bags, coats, and quilting. Goose feathers are preferred because they are soft. Manufacturers often mix goose feathers with down feathers to provide extra softness. Answer: softness
Output:
Why are goose feathers preferred for stuffing by manufacturers?