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: a pulley is used for lifting objects. 
Sentence2: Resistance exercises are weight-lifting exercises.

SOLUTION: lifting

PROBLEM: Sentence1: hiding can be used for avoiding predators. 
Sentence2: Camouflage is used for avoiding predators.

SOLUTION: avoiding

PROBLEM: Sentence1: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: Fishers are predators that can eat porcupines.

SOLUTION:
predators