Which of the following solutions are isotonic with respect to 0.5 M NaCl solution having degree of dissociation = 0.8. (a) 153.9 gm of Sucrose dissolved in 500 ml of solution. (b) 0.3 M aQ. NaSO4 solution undergoing 100 % ionization (c) 1.8 % w/w aQ. NaOH solution undergoing 100 % ionization. (d) 1.2 M benzoic acid in a solution of benzene where the acid dimerizes to an extent of 50 %.