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


[Q]: Sentence1: Ice is frozen water. 
Sentence2: ice expands.
[A]: Ice


[Q]: Sentence1: Energy enters ecosystems in the form of sunlight or chemical compounds. 
Sentence2: Energy enters biomes in the form of sunlight or chemical compounds.
[A]:
Energy