Answer;
A. Blood
Explanation;
The main organs of the Circulatory system are the heart, the brain, the lungs. There are other key things like arteries, veins, and capillaries but they are not organs.
The major tissues in the circulatory system are the epithelial, muscle, nervous, and connective tissues.
Blood is the main connective tissue in the circulatory system, but it's a liquid connective tissue. Blood tissue is in the same family as bone and cartilage, but instead it has a liquid medium that holds it together.
Answer:
nonhuman animals models
Explanation:
A surrogate is defined as a substitute for another person to play a specific role in any given arrangement.
In the case of laboratory research non- human animal models are often used as surrogates for humans to conduct research.
For conducting research a lot of ethical concerns are raised when conducting experiments on human beings and hence, the scientists had to look for alternatives.
The non-human animals have emerged as great alternatives for the humans to conduct research and thanks to the genome sequences that are now known the list of animal models have increased greatly and we are further sure that there are several similarities that these animal models share with humans and thus, the results obtained by conducting research on them are considered reliable.
Answer:
I think the answer would be A.