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: Female monotremes lack a uterus and vagina. 
Sentence2: Babies are normally delivered from the uterus through the vagina.

A: uterus
****
Q: Sentence1: Sex hormones are chemical messengers that control sexual development and reproduction. 
Sentence2: Androgens are male sex hormones.

A: Sex
****
Q: Sentence1: air pollution can cause the pH of soil to decrease. 
Sentence2: Air pollution can cause a decrease in crop yields.

A:
air
****