(b) Density is directly proportional to mass. Molar mass are CCl4→12+142=154gmol−1 ‌n−C3H7I→12×3+7×1+127=170gmol−1 ‌n−C3H7‌Br→12×3+7×1+80=123gmol−1 ‌n−C3H7‌Cl→12×3+7×1+35.5=78.5gmol−1 As molar mass of n−C3H7I is highest, so its density will be highest too.
