Smith ______ a book about China last year, but I don't know whether he has finished it.

A．has wrote

B．wrote

C．had written

D．was writing

土地价值的计算公式为( )。

A．土地机会成本=土地影子费用+新增资源消耗

B．新增资源消耗=土地机会成本+土地影子费用

C．土地影子费用=土地机会成本-新增资源消耗

D．土地影子费用=土地机会成本+新增资源消耗