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: an automobile engine transforms chemical energy into mechanical energy. 
Sentence2: cars transform chemical energy into mechanical energy.

SOLUTION: chemical

PROBLEM: Sentence1: Mammals that are viviparous are called therian mammals. 
Sentence2: Mouse-sized viviparous mammals evolved by Jurassic times.

SOLUTION: Mammals

PROBLEM: Sentence1: Bile, produced by the liver, helps fat digestion and absorption. 
Sentence2: the liver helps reduce acidity of food.

SOLUTION:
liver