D. Estuaries
Estuaries are a place where fresh and salt water mix.
Answer:
four
Explanation:
Carbon atoms have four electrons in their outer shell. So, it exhibits tetravalency & thus, a single carbon atom can form a maximum of four (4) bonds with other atoms
Answer:
1.It helps to digest our food.
2.It is used as antibiotics to treat bacterial infection and disease.
3.It is used by humans to create food products such as cheese, yoghurt, pickles, soy sauce and vinegar.
4.It is use to break down our sewage and to clean up oil spills..