I think the answer is D but it's been a while since I've done this.
D. Estuaries
Estuaries are a place where fresh and salt water mix.
Answer:
Biology can simply be described as the study of living organisms. Biology is divided into many sub categories depending on the features of life that we want to study. For example, molecular biology is the study of molecules which make up living organisms.
Zoology can be described as a branch of biology under which animals are studied. The field of zoology involved studying the taxonomy of animals, their evolutionary histories, physiology, embryology etc. All these studies are parts of biology hence zoology and biology are related.
Apart from these other unifying principles shared between zoology and biology are genetics, cell biology, population biology,biochemistry etc.
