What is the role played by the renin-angiotensin mechanism in the regulation of kidney function?

• A
  It decreases blood pressure and reduces $GFR$.
• B
  It activates $JG$ cells to release renin,which increases $GFR$ and stimulates aldosterone secretion.
• C
  It inhibits the reabsorption of $Na^+$ and water from the $DCT$.
• D
  It causes vasodilation of the afferent arteriole,decreasing glomerular pressure.