双下肢中枢性瘫痪（）

A.高颈段脊髓病变

B.脊髓颈膨大病变

C.胸段脊髓病变

D.脊髓腰膨大病变

E.骶段脊髓病变

We didn’t arrive at school on time yesterday morning ________ the heavy snow.

A．because

B．because of

C．so

D．so that