Question

aging occurs when... cells fail to copy dna accurately. cells miss their cue to exit the cell cycle. cells exit the cell cycle and stop dividing completely. cells live too long.

Explanation:

Aging is associated with cells exiting the cell cycle and stopping division completely. This is a key aspect of the aging process at the cellular level. Cells that fail to copy DNA accurately can lead to mutations (related to cancer etc. more than aging in this context). Cells missing their cue to exit the cell cycle would keep dividing (like cancer cells). Cells living too long is not the direct cause of aging in the context of the standard cellular aging theory.

Answer:

cells exit the cell cycle and stop dividing completely.