多项式4a3-a2b2-43ab是4次3项式,次数最高项的系数是-1.
Nick ______ a new camera. He has taken lots of pictures with it. [ ]
A. buys
B. is buying
C. bought
D. will buy
位于前庭襞下方的喉腔部位是
A.喉口B.喉前庭C.前庭裂D.声门裂E.喉室