Explanation

(a)
(a) Density of water = $1g\ {cm}^{- 3}$
Mass of water=$1\ m^{3} = 10^{6}$ $cm^{- 3}$
Mass = $volume \times density$
= $10^{6}{cm}^{- 3} \times 1\ g\ {cm}^{- 3}$
=$10^{6}$
= $\frac{10^{6}}{10^{3}}kg$
= 1000 kg
(b) Mass of normal adult man = 65 kg
(c) Density of Hg = $13.6\ g\ {cm}^{- 3}$
Volume of Hg = $10L = 10 \times 1000\ {cm}^{- 3}$
$\therefore Mass\ of\ Hg = 13.6 \times 10 \times 1000$
= 136000 g
= 13.6 kg
$\therefore Mass\ of\ 1m^{3}\ water\ is\ highest.$