Solution A, B, C and D are respectively 0.1M Glucose, 0.05M NaCl, 0.05M BaCl₂ and 0.1M AlF₃. Which one of the following pairs is isotonic ?

The solutions A (0.1 M glucose) and B (0.05 M NaCl) are isotonic. 
They have the same osmotic pressure. The product of molar concentration and the number of ions obtained on dissociation of 1 molecule of solute is the same for both solutions. Glucose is non-electrolyte and does not dissociate. Hence the product will be, 0.1×1 = 0.1 
One molecule of NaCl dissociates to give two ions, 
Hence the product  is 0.05×2 =0.1