The famous writer______one new book in the past two years.[ ]

A. is writing  

B. was writing  

C. wrote  

D. has written

SO₃具有强吸水性，接触湿空气后生成白雾，其主要成分是（）。

A.盐酸

B.磺酸

C.硫酸

D.醋酸