填空题

[听力原文]
People are living longer and longer. As a result, more and more middle-aged adult have to take care of their aging parents. When their parents can no longer care for themselves, these adults may be forced to stay at home to care for them. Taking care of aging parents is quite difficult. For example, an aging parent may become blind. He or she needs children to perform a lot of everyday work. The roles of parents and children are being changed. When children find it difficult to take care of their dependant parents, they often decide to take them to a nursing home.
There, proper care and attention can be given. This allows the children to return to their normal, everyday life.

Why do more middle-aged adults have to take care of their aging parents
Because people are living（）