The correct answer is option A , sensory system.
A human body primarily consists of the following organ systems :
Circulatory, Respiratory, Digestive, Excretory, Nervous and Endocrine systems, Immune, Integumentary, Skeletal, Muscle and Reproductive systems.
There is no as such sensory system. However the neurology based system is called Nervous system which includes organs and their processing in the sensing of stimulation.
Succession is a thing that happens to forests or other ecosystem landscapes.
The first one is commensalism. The second one is mutualism. The last one is parasitism.
Yes, because the envelope can be a important document- so therefore it can be considered "confidential".
