Plasma osmolarity is maximally affected by-

Ans. is 'a' i.e., Na+ * Normal osmolarity of (extracellular) body fluids is about 290 mOsm/L.* Important contributors of body fluid osmolarity areConstituentConcentration mMole/LNa+135-155Cr90-110HCO3-25K+3[?]5 - 5[?]0Glucose34 - 5[?]6 mmole/L (60-100 mg/dl)BUN3[?]6 - 7[?]1 mmole/L (10-20 mg/dl)