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: Telephone Telephone calls are expensive. 
Sentence2: Communicating by transmitting sound is expensive.

SOLUTION: expensive

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

SOLUTION: avoiding

PROBLEM: Sentence1: electric devices require electrical energy to function. 
Sentence2: Lie detectors are electrical or mechanical devices.

SOLUTION:
devices