听力原文： A potato farmer was sent to prison just at the time when he should have been digging the ground for planting the new crop of potatoes. He knew that his wife would not be strong enough to do the digging by herself, but that she could manage to do the planting and he knew that he did not have any friends or neighbors who would be willing to do the digging for them. So he wrote a letter to his wife which said, 'Please do not dig the potato field. I hid the money and the gun there.' Ten days later he got a letter from his wife. It said, 'I think somebody read your letter before it got out of the prison. Someone arrived here two days ago and dug up the whole potato field. What shall I do now?' The prisoner wrote back at once, 'Plant the potatoes, of course.' (30)