Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

[Q]: Sentence1: Cell death occurs by activation of cell death genes. 
Sentence2: Aging is associated with the activation of certain genes.
[A]: activation


[Q]: Sentence1: Ozone depletion results in higher levels of UV radiation reaching Earth. 
Sentence2: less ozone means more ultraviolet light.
[A]: Ozone


[Q]: Sentence1: Bone is less flexible than cartilage but stronger. 
Sentence2: bone is less flexible than chondrocytes.
[A]:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Bone


