d
Let initial activity \(=\mathrm{N}_{0}=0.8\, \mu \mathrm{ci}\)

\(0.8 \times 3.7 \times 10^{4}\, \mathrm{dps}\)

Activity in \(1\, \mathrm{cm}^{3}\) of blood at \(\mathrm{t}=10\, \mathrm{hr}\)

\(\mathrm{n}=\frac{300}{60} \mathrm{dps}=5 \,\mathrm{dps}\)

\(\mathrm{N}=\) Activity of whole blood at timet \(=10 \,\mathrm{hr}\) Total volume of the blood in the person, \(V\)

\(=\frac{N}{n}\)

\( = \frac{{{N_0}e - \lambda t}}{n} = \) \( \frac{{0.8 \times 3.7 \times {{10}^4} \times 0.7927}}{5} \cong 5\,\,{\mkern 1mu} litre\)