根据《地规》第8.2.11条

$$ e < 0. 4 < \frac {2 . 6}{6} = 0. 4 3 \mathrm{m} $$

$$ a ^ {\prime} = b ^ {\prime} = 1. 4 \mathrm{m} $$

$$ \begin{array}{r l} M _ {\mathrm{II}} & = \frac {1}{4 8} \left(l - a ^ {\prime}\right) ^ {2} \left(2 b + b ^ {\prime}\right) \left(p _ {\mathrm{jmax}} + p _ {\mathrm{jmin}}\right) \\ & = \frac {1}{4 8} \times (2. 6 - 1. 4) ^ {2} \times (2 \times 2. 6 + 1. 4) \times (1 7 0 + 2 0 0) = 7 3. 2 6 \mathrm{kN} \cdot \mathrm{m} \end{array} $$

因此选（C）