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.

Q: Sentence1: propulsion is used for flying by a spacecraft. 
Sentence2: When Apollo 12 took off, the spacecraft was hit by lightning.

A: spacecraft
****
Q: Sentence1: the Earth being tilted on its rotating axis causes seasons. 
Sentence2: the planet's orbit and tilt causes seasons.

A: seasons
****
Q: Sentence1: Sepals are usually green, which camouflages the bud from possible consumers. 
Sentence2: The enclosure of the lower part of the flower is usually green.

A:
green
****