预后比较严重的脊椎骨折是（）
A.横突骨折
B.椎体压缩骨折
C.椎体骨折片嵌入椎管内
D.棘突骨折
E.肋、椎关节分离
参考答案：B
They are still very cautious about ________ side effect the new medicine will bring about, although the experts have tried it on about 2000 patients．
A．which
B．that
C．where
D．what
照准误差主要取决于什么？
