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: a light bulb is used for seeing in the dark. 
Sentence2: light is required for seeing.
[A]: seeing


[Q]: Sentence1: Some birds are pollinators that co-evolved with plants. 
Sentence2: insects pollinate plants.
[A]: plants


[Q]: Sentence1: Skin color is another polygenic trait. 
Sentence2: Skin color is a trait controlled by several genes.
[A]:
Skin