What is the rarest blood type?

AB Negative

Explanation:

AB Negative is the rarest of the eight blood types - just 1% of our donors have it. Despite being rare, demand for AB negative blood is low and we don't struggle to find donors with AB negative blood. However, some blood types are both rare and in demand.

so we know the answer cannot be c because no insect or animal starts as an adult

the answer is a. a swimming larvae

because since they are sea animals they automatticaly have to know how to swim they cannot just sink to the bottom

sorry if this is the incorrect answer.