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: Cows are social animals. 
Sentence2: when a cow moves, chemical energy is converted to mechanical energy.

SOLUTION: Cows

PROBLEM: Sentence1: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: humans have collected and grown porcinis for thousands of years.

SOLUTION: Humans

PROBLEM: Sentence1: Flowers produce seeds for reproduction. 
Sentence2: flowers require dispersal for reproduction.

SOLUTION:
Flowers