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.

[EX Q]: Sentence1: Homogeneous mixtures are called solutions. 
Sentence2: A homogenous mixture is formed when one substance dissolves in another.
[EX A]: Homogeneous

[EX Q]: Sentence1: Antibiotics and vaccines are being stockpiled as Britain gears up to meet the bioterrorism threat. 
Sentence2: Antibiotics and vaccines are being stockpiled against another potential threat in the environment.
[EX A]: Antibiotics

[EX Q]: Sentence1: plant reproduction often requires pollen. 
Sentence2: Pollen grains contain the male gametes in sexually reproducing plants.
[EX A]:
pollen