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: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Sentence2: Fossils of a water animal or plant are located in water-laid sediments.

SOLUTION: animal

PROBLEM: Sentence1: Chordates have a complete digestive system and a closed circulatory system. 
Sentence2: All chordates are vertebrates.

SOLUTION: Chordates

PROBLEM: Sentence1: Folds are usually caused by compressional forces. 
Sentence2: compressional force causes an object to change shape.

SOLUTION:
compressional