A/an or the.He changes .... sheep for .... goose. He changes .... goose for .... hen. He changes ...hen for apples.The old man brings .... apples to his wife. He gets some money from ....Englishman.

He changes the sheep for a goose. He changes the goose for a hen. He changes the hen for apples. The old man brings the apples to his wife. He gets some money from an Englishman. В тексте нет конкретики - поэтому возможны варианты использования артиклей.