根据《混规》第 11.6.3 条

$$ \eta_ {\mathrm{j}} = 1. 0, \quad b _ {\mathrm{j}} = b _ {c} = 7 0 0 \mathrm{mm}, \quad h _ {\mathrm{j}} = 7 0 0 \mathrm{mm} $$

$$ V _ {\mathrm{u}} = \frac {1}{\gamma_ {\mathrm{RE}}} (0. 3 \eta_ {\mathrm{j}} \beta_ {\mathrm{c}} f _ {\mathrm{c}} b _ {\mathrm{j}} h _ {\mathrm{j}}) = \frac {1}{0 . 8 5} (0. 3 \times 1. 0 \times 0. 9 3 3 \times 2 7. 5 \times 7 0 0 \times 7 0 0) = 4 4 3 7 \mathrm{kN} $$

因此选（C）