Given a text T, and several options, according to the question posed in the text T to choose the most appropriate option from the options as the answer, please directly output the most appropriate option, do not need to output the explanation.

Stereo Warehouse is a US retailer that offers employees a defined benefit pension plan and stock options as part of its compensation package. Stereo Warehouse prepares its financial statements in accordance with US GAAP.Peter Friedland, CFA, is an equity analyst concerned with earnings quality. He is particularly interested in whether the discretionary assumptions the company is making regarding compensation plans are contributing to the recent earnings growth at Stereo Warehouse. He gathers information from the company's regulatory filings regarding the pension plan assumptions in Exhibit 4 and the assumptions related to option valuation in Exhibit 5.
| Exhibit 4.Assumptions Used for Stereo Warehouse Defined Benefit Plan |
| 200920082007 |
| Expected long-term rate of return on plan assets6.06%6.14%6.79%Discount rate4.854.945.38Estimated future salary increases4.004.444.25Inflation3.002.722.45 |

| Exhibit 5.Option Valuation Assumptions |
| 2009 | 2008 | 2007 |
| Risk-free rate | 4.6% | 3.8% | 2.4% |
| Expected life | 5.0yrs | 4.5yrs | 5.0yrs |
| Dividend yield | 1.0% | 0.0% | 0.0% |
| Expected volatility | 29% | 31% | 35% |


 
Compared to the assumptions Stereo Warehouse used to value stock options in 2008, earnings in 2009 were most favorably affected by the change in the:
Option A:expected life.
Option B:risk-free rate.
Option C:dividend yield.

Answer: C