By the time that the young bear grew to full adulthood , his parents and siblings had moved on to better hunting and fishing grounds . Yet , alas , the young bear still had an attachment to this place that he called home - as it was really the only home that he had ever known . Years went by .

Q with options: Give answer the following question using evidence from the above passage: Why did the young bear 's family move on to better hunting and fishing grounds ?
Available choices:
(a). None of the above choices .;
(b). The place they all lived never ran out of prey as time passed .;
(c). The place they all lived had a lot of prey for them to eat .;
(d). The place they all lived ran out of prey as time passed .;
(d).