-What's this in English?

-______.[ ]

A. It's dictionary.    

B. This is a backpack.    

C. It's a ruler.        

D. This is book.

扁平颅底主要是颅地扁平使蝶骨体长轴与枕骨斜坡构成的颅底角度变大，根据头颅X线侧位片检查，颅底角大于多少度有临床诊断意义（）

A.>135°

B.>140°

C.>145°

D.>150°

E.>155°