根据《混规》第7.1.2、7.1.4条

$$ q = 2 8 + 0. 5 \times 8 = 3 2 \mathrm{kN/m} $$

$$ M _ {\mathrm{q}} = 0. 1 2 5 \times 3 2 \times 8 ^ {2} = 2 5 6 \mathrm{kN} \cdot \mathrm{m} $$

$$ \sigma_ {\mathrm{sq}} = \frac {M _ {q}}{0 . 8 7 h _ {0} A _ {\mathrm{s}}} = \frac {2 5 6 \times 1 0 ^ {6}}{0 . 8 7 \times 6 1 0 \times 4 \times 4 9 1} = 2 4 5. 6 \mathrm{N} / \mathrm{mm} ^ {2} $$

$$ \rho_ {\mathrm{te}} = \frac {A _ {\mathrm{s}}}{A _ {\mathrm{te}}} = \frac {4 \times 4 9 1}{0 . 5 \times 2 5 0 \times 6 5 0} = 0. 0 2 4 > 0. 0 1 $$

$$ \psi = 1. 1 - 0. 6 5 \frac {f _ {\mathrm{tk}}}{\rho_ {\mathrm{te}} \sigma_ {\mathrm{sq}}} = 1. 1 - 0. 6 5 \times \frac {2 . 0 1}{0 . 0 2 4 \times 2 4 5 . 6} = 0. 8 8 $$

因此选（C）