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: Every photograph is produced by a camera. 
Sentence2: Photographers record images.

SOLUTION: photograph

PROBLEM: Sentence1: Mollusks are invertebrates such as the common snail. 
Sentence2: Gastropods are snails and slugs.

SOLUTION:
snail