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: plant requires seed dispersal for reproduction. 
Sentence2: plants are pollinated by birds.

SOLUTION: plant

PROBLEM: Sentence1: Heat production is increased by shivering and non-shivering thermogenesis . 
Sentence2: Heat production occurs when many muscles contract a little bit all at once.

SOLUTION: Heat

PROBLEM: Sentence1: the vanes rotating in an electric fan causes air to move. 
Sentence2: Fans move air, providing a cooling breeze.

SOLUTION:
air