若一个多边形的各个外角都等于30°,则这个多边形的边数是( )
A.4
B.6
C.12
D.24
360°÷30°=12,
∴多边形的边数是12.
故选C.
经下颌颈层面上位居断面中央的是
A.胼胝体上方B.胼胝体压部C.中脑D.鞍上池E.鼻咽
This chemical is made()a special formula.
A. from
B. of
C. according to
D. in