我国栽培梨的品种主要划分为秋子梨系统、白梨系统、洋梨系统和( )系统。
A．油梨系统
B．沙梨系统
C．莱阳梨系统
D．京梨系统
参考答案：B
烧结矿的合格品
It will cost $ 20000 a year for four years when an 8 - year old child is ready for college. How much should be invested today if the child will make the first of four annual withdrawals 10 - years from today The expected rate of return is 8 percent.（）
A. $ 30683.
B. $ 66243.
C. $ 33138.
