ABC Investments has purchased a new computer system for $1.4 million and decided to depreciate it over a 4-year period on a sum-of-years’ digits (SYD) method. ABC estimates that the salvage value will be $ 200000 at the end of the four years. What will be the depreciation expense for the third year（）

A. $ 300000.

B. $ 240000.

C. $186000.

如图为吞噬细胞杀灭病菌的示意图，请据图回答：

在体液免疫中，吞噬细胞在吞噬病菌后，还能对其进行处理，暴露出这种病原体所特有的（），并将抗原呈递给T细胞，T细胞再将抗原传递给B细胞，B细胞受到刺激后，经增殖并分化为（）细胞和（）细胞。