You seem to have answered the question within its-self, R is the answer i believe.<span />
The kidneys filter the blood to remove waste products, which they convert into urine. Urine is carried from each kidney, through a tube called a ureter to the bladder, where it is stored. The ureter and blood vessels enter and exit the kidney through the renal hilum.
Question:
A joint produces movement when its angle decreases.
Answer:
It is B, rotation because it allows the joint to rotate.
