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: Amphibians are the first true tetrapods, or vertebrates with four limbs. 
Sentence2: Frogs are classified as amphibians.

SOLUTION: Amphibians

PROBLEM: Sentence1: a flashlight converts chemical energy into light energy. 
Sentence2: Only as long as there are batteries in the flashlight, the flashlight will function.

SOLUTION: flashlight

PROBLEM: Sentence1: Pollen consists of tiny grains that are the male gametes of plants. 
Sentence2: Pollen seeds come from male gametes of plants.

SOLUTION:
Pollen