问题如下：
Considering the following statements about capital strcture and leverage, which is least accurate?
选项：
A.Operating leverage decreases when the proportion of firm's total costs in fixed costs decreases.
B.Capital structure decisions are affected by the corporate tax rate
C.Operating leverage increases with the corporate tax rate.
解释：
C is correct.
Operating leverage decreases when fixed costs account for a smaller percentage of total costs.
The lower the tax rate, the higher the after-tax cost of debt. Thus it may influence the capital structure.
Operating leverage is not affected by the corporate tax rate.
能不能从定义出发理解，ops leverage直接是随着 FC 的变化而变化的？
