Given below are two statements. One is labelled as Assertion A and the other labelled as Reason R.  

Assertion (A) : A fall in glomerular blood flow/glomerular blood pressure can activate the JG cells to release renin.

Reason (R) : Atrial natriuretic factor can cause vasodilation and thereby decrease blood pressure.  

In light of the above statements, choose the most appropriate answer from the options given below. 

Both A and R are correct but R is not the correct explanation of A. 

A fall in glomerular blood flow or glomerular blood pressure can activate the juxtaglomerular (JG) cells to release renin. Renin, in turn, initiates the renin-angiotensin-aldosterone system (RAAS), leading to vasoconstriction and an increase in blood pressure.
Atrial natriuretic factor (ANF) does indeed cause vasodilation, resulting in a decrease in blood pressure. ANF is secreted by the heart's atria in response to increased blood volume and pressure, serving as a counter-regulatory mechanism to reduce blood pressure.