###Rationale: Macula densa sense both Na+ and Cl- , but Cl- is more important.

###Answer: OPTION C IS CORRECT.
###Question: The tubuloglomerular feedback is me­diated by:
###Options:
A. Sensing of Na+  concentration in the macula densa
B. Sensing of HCO3 - concentration in macula densa
C. Sensing NaCl concentration in the macula densa
D. Opening up of voltage gated Na+ channels in afferent arteriole
