题目内容：
【单选题】The asset section of the January 1, 20X9, balance sheet of Big Valley Company includes a machine which was acquired on January 1, 20X5. The machine.s original cost was $500,000, and the estimated life was determined to be 10 years. The estimated residual value was zero, and the straight-line method of depreciation was chosen. The book value of the machine as of January 1, 20X9, is:
A、9%
B、14.4%
C、18%
D、35%
参考答案：