换热站是用来改变供热介质（），分配、控制及计量供给用户（）的设施。
参考答案：参数；热能
若f（x）sinx是周期为π的奇函数，则f（x）可以是（ ）
A．sinx
B．cosx
C．sin2x
D．cos2x
An investor has gathered the following data, presented on an annual basis, for an apartment complex that is being considered for purchase: Gross potential rental income $176000 Insurance and taxes$15000 Utilities $11400 Repairs and maintenance $17350 Depreciation$21000 The annual net operating income (NOI) for the apartment complex is closest to:（）
A. $100000.
B. $116000.
C. $132250.
