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.

[EX Q]: Sentence1: cell division often causes growth. 
Sentence2: Cell division leads to reproduction.
[EX A]: cell

[EX Q]: Sentence1: Telephone Telephone calls are expensive. 
Sentence2: Communicating by transmitting sound is expensive.
[EX A]: expensive

[EX Q]: Sentence1: Invertebrates are animals that lack a vertebral column, or backbone. 
Sentence2: Many invertebrates have an exoskeleton.
[EX A]:
Invertebrates