(c)
Weight of pure NaCl=$6.5 \times 0.9 = 5.85$ g
No. of equivalent of NaCl$= \frac{5.85}{58.5} = 0.1$
No. of equivalent of NaOH obtained=0.1
Volume of 1 M acetic acid required for the neutralisation of
$NaOH = \frac{0.1 \times 1000}{1}$
$= 100\ cm^{3}$