Answer: A substance is matter which has a specific composition and specific properties. Every pure element is a substance. Every pure compound is a substance. Examples of substances: Iron is an element and hence is also a substance.
Explanation:
The kidneys make two main hormones, vitamin D and erythropoietin. Vitamin D is essential for a number of different functions in the body. Most of the vitamin D that is in the blood is inactive and it is modified by the kidney and other tissues to activate it.
Cells are the most simple level of organization, as tissues contain cells, organs contain tissues and systems contain organs, so R would be your answer.
Answer:
The corpus callosum
Explanation:
The corpus callosum is the largest white matter structure in the brain. It is located beneath the cerebral cortex and it connects the left and right cerebral hemispheres thus enabling communication between them. The corpus callosum is a bundle of nerve fibers, (axon projections) which transmits neural signals.
