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.
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Question: Sentence1: Telephone Telephone calls are expensive. 
Sentence2: Communicating by transmitting sound is expensive.

Answer: expensive


Question: Sentence1: igneous rocks are formed from magma cooling. 
Sentence2: magma solidifies into igneous rocks.

Answer: magma


Question: Sentence1: Like proteins, DNA and RNA are polymers of various small chemically related molecules. 
Sentence2: polymers of various small chemically related molecules can squeeze through pores in the nuclear membrane.

Answer:
chemically