Answer: The correct answer for the fill in the blank is B. Organs.
Tissue is formed by cluster of similar cells. Similarly, various tissue organised in a particular area to perform a specific task, combine to form organ. Organ is one of the levels of structural organization in the human body.
Example- Heart is an organ of circulatory system. It comprises of muscle tissue ( cardiac muscle or myocardium) and connective tissue ( endocardium and pericardium).
This organ helps in the circulation of oxygenated blood throughout the body.
