Your father has type b blood. your mother has type o blood. you get tested and learn that your blood is also type o. what does this tell you

Since the father is has type b blood, this means he has both b and o alleles. The mother has o type blood which means she only has the o allele. This tells us that the parents each passed down an o allele to the child that's why he has type o blood. 

I’d say a : water molecules

Digestion because it removes waste