44. 如右圖所示之桁架,其BD桿件之內力為何?(A) $10\mathrm{kN}$ (拉力)(B) $10\mathrm{kN}$ (壓力)(C) $10\sqrt{2}\mathrm{kN}$ (拉力)(D) $10\sqrt{2}\mathrm{kN}$ (壓力)