38.於空間平行力系中,若各力量皆平行於 x 軸,則下列何者為平衡時所需的條件?(A) ΣFx = 0,ΣMy = 0,ΣMz = 0 (B) ΣFy = 0,ΣMx = 0,ΣMz = 0(C) ΣFz = 0,ΣMx = 0,ΣMy = 0 (D) ΣMx = 0,ΣMy = 0,ΣMz = 0