$^{\pi} C_{2} H_{3} O H$ $=1 \times 0.500 \times R \times T=0.5 R T$

$^{\pi} M g_{3}\left(P O_{4}\right)_{2}$ $=5 \times 0.100 \times R \times T=0.5 R T$

$^{\pi} K B r=2 \times 0.250 \times R \times T=0.5 R T$

$^{\pi} N a_{3} P O_{4}=4 \times 0.125 \times R T=0.5 R T$

since the osmotic pressure of all the given solutions is equal.

Hence all are isotonic solution.