Task: Question Generation
Input (English):  In The Flopsy Bunnies, Benjamin Bunny and Peter Rabbit are adults, and Benjamin has married his cousin Flopsy. The couple are the parents of six young rabbits generally called The Flopsy Bunnies. Benjamin and Flopsy are "very improvident and cheerful" and have some difficulty feeding their brood. At times, they turn to Peter Rabbit (who has gone into business as a florist and keeps a nursery garden), but there are days when Peter cannot spare cabbages. It is then that the Flopsy Bunnies cross the field to Mr. McGregor's rubbish heap of rotten vegetables.
One day they find and feast on lettuces that have shot into flower, and, under their "soporific" influence, fall asleep in the rubbish heap, though Benjamin puts a sack over his head. Mr. McGregor discovers them by accident when tipping grass-clippings down and places them in a sack and ties it shut then sets the sack aside while attending to another matter. Benjamin and Flopsy are unable to help their children, but a "resourceful" wood mouse called Thomasina Tittlemouse, gnaws a hole in the sack and the bunnies escape. Their parents fill the sack with rotten vegetables, and the animals hide under a bush to observe Mr. McGregor's reaction.
Mr. McGregor does not notice the substitution, and carries the sack home, continually counting the six rabbits. His wife claims the skins for herself, intending to line her old cloak with them, but when she reaches into the sack and discovers the rotten vegetables she becomes very, very, angry and accuses her husband of playing a trick on her. And then, Mr. Mc Gregor becomes very angry too, and he throws a rotten vegetable marrow out through the window, hitting the youngest of the eavesdropping bunnies who has been sitting on the window-sill (leaving the Mc Gregors to argue). Their parents decide it is time to go home. At Christmas, they send the heroic little wood mouse a quantity of rabbit-wool. She makes herself a cloak and a hood, and a muff and mittens.
Scholar M. Daphne Kutzer points out that Mr. McGregor's role is larger in The Flopsy Bunnies than in the two previous rabbit books, but he inspires less fear in The Flopsy Bunnies than in Peter Rabbit because his role as fearsome antagonist is diminished when he becomes a comic foil in the book's final scenes. Nonetheless, for young readers, he is still a frightening figure because he has captured not only vulnerable sleeping bunnies but bunnies whose parents have failed to adequately protect them.
Output (English): What does Benjamin and Flopsy fill the sack with after the bunnies escape?