抗拔承载力：$T_{uk}=\sum\lambda_i q_{sik}u_i l_i=0.7\times\pi\times0.4\times(30\times2+40\times8+40\times12+80\times2)=0.8792\times(60+320+480+160)=0.8792\times1020=896.8\mathrm{kN}$，$G_p=2.49\times24=59.76\mathrm{kN}$，$N_k\le T_{uk}/2+G_p=448.4+59.8=508.2\mathrm{kN}$。裂缝控制：环境类别三类，预应力管桩裂缝控制等级一级，$\sigma_{ck}-\sigma_{pc}\le0$，$N_{ck}\le\sigma_{pc}A_0$，$A_0=\frac{\pi}{4}(400^2-210^2)=3.14/4\times(160000-44100)=0.785\times115900=90981\mathrm{mm^2}$，$N_{ck}\le4.9\times90981=445.8\mathrm{kN}$。取小值445.8，选B。