Explanation

(c)
Osmotic pressure is a colligative property . More the number of particles (or ions) in solution, more will be osmotic pressure.
Nacl solution
Given , mass of NaCl =7 g V=1L
$\therefore$ Concentration
=$\frac{mass}{mol.mass\ } = \frac{7}{58.5} = 0.119\ M$
NaCl dissociates as follows
NaCl $\rightarrow \ \ Na^{+}Cl^{-}$(2 ions)
$\therefore$ Concentration of ions in solution
=2$\times 0.119\ M$
=0.0238 M
MgCl solution
Given, mass of$MgCl_{2}$=7g, V=1L
$\therefore$ Concentration=$= \frac{mass}{mol.mass} = \frac{7}{95} = 0.0747$
$MgCl_{2}$ dissociates as follows
MgC$l_{2} \rightarrow Mg^{2} + 2Cl^{-}$ (3 ions)
$\therefore\ \ \$Concentration of ions in solution =3$\times$0.074 M
=0.222 M
$\because$ Number of particles in solution B(NaCl)are more than in solution A. $\therefore$ Osmotic pressure of solution B(NaCl) will be more than solution A.