On 1 January, Hellen’s portfolio is valued at $1000000. Hellen want to make a $100000 payment to buy a house on 31 December of the same year, but does not want the year-end portfolio value to fall below $1000000. The expected annual return on the investor’s existing portfolio is 15 percent with an expected standards deviation of 20 percent. The risk-free rate is 8%. The safety-first ratio for the portfolio is closest to:（）

A. 0.10.

B. 0.25.

C. 0.35.

下列外力作用表现形式，按发生时间由先到后排列，依次是（）

A、风化→侵蚀→搬运→堆积

B、侵蚀→堆积→风化→搬运

C、侵蚀→风化→搬运→堆积

D、风化→堆积→搬运→侵蚀