1, O because if either shows present it's O.
Answer:
The immune system protects the host from pathogenic organisms (bacteria, viruses, fungi, parasites). To deal with this array of threats, the immune system has evolved to include a myriad of specialised cell types, communicating molecules and functional responses.
Explanation:
The first choice is correct
Essential services, such as water purification, nutrient cycling, and plant pollination are all examples of earth's Ecosystem services.
The ecosystem is defined as the interaction between the biological communities with its physical environment. The services provided by the ecosystem are termed as ecosystem services. The ecosystem with the help of its different components performs water filtration, recycling of the nutrients, pollination, seed dispersal etc. These all services provided by the ecosystem comes under the category of ecosystem services.
There is the digestive system is used to help you digest food.
The respiratory system that lets us use and brain oxygen.
Lastly, the circulatory system which allows our bodies to have flowing blood.
