It is B. Because you cannot give internal fertilization/ live birth inside.
I think it'd be cell, tissue, organ, organ system, organism.
I hope this helps!
Answer: Option D.
Rate of oxygen consumption.
Explanation:
Volume of oxygen used or Vo2 Max is the maximum ability of a person to consume oxygen and the ability of the heart, lungs and blood to transport the oxygen to other tissues and utilize it to produce ATP or energy during intense exercise.
1. They are easy to raise.
2. Have many offspring during per mating.
3. It can fertilize itself.
4. It has varieties in genotype that is easy observable.
5. It has phenotype that is also easy observable.