TASK DEFINITION: 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.
PROBLEM: Sentence1: Skin color is another polygenic trait. 
Sentence2: Skin color is influenced by multiple genes.

SOLUTION: Skin

PROBLEM: Sentence1: riding a bike does not cause pollution. 
Sentence2: riding a bike does not release particles.

SOLUTION: bike

PROBLEM: Sentence1: The addition of salt increases the density of water. 
Sentence2: Increasing the density of water decreases its melting point.

SOLUTION:
density