Winthur Publishing Company invests $ 800000 in a printing press that will be depreciated on a straight-line basis over four years and will have a zero salvage value at the end of its life. Sales revenues, operating expenses, and net income for each year are shown in the table below.（）

A.$18.75

B.$15.75

C.$12.75

我国喀斯特地貌发育最完美、分布最集中的区域是（）地区。

A.青藏高原及其边缘

B.黄河中下游

C.云贵高原及其边缘

D.长江中下游