单项选择题 John Jones has decided to go into the business of pro-ducing and selling boats. In order to begin this venture,he must invest $10 million in a boat production plant.The cost to produce each boat will be $7,000, and theselling price will be $20,000. Accounting for the costof the production plant, which of the following expres-sions represents the profit, in dollars, that John willrealize when xboats are produced and sold?A.13,000x-10,000,000B.27,000x-10,000,000C.9,973,000xD.20,000xE.13,000x

单项选择题 鼻唇角指的是A.鼻小柱前端至鼻底与鼻底至上唇红间 的角B.鼻背与前额至鼻根间斜面交角C.鼻根垂线与鼻背线的夹角D.鼻背线与鼻小柱线的夹角E.头侧位于眼耳平面时鼻小柱线与水平线的夹角

单项选择题 如图所示的半圆环体，其体积为()。