问题如下：
Recently Analyst Bob is studying regulatory environment in a country. 4 years ago, the country advocates environment-friendly power generation. So the government increases taxes on coal fuel and provides subsidies on solar power and wind power generation. Bob finds some changes in electricity generation production as following table shows.
According to the table, which government policy is most effective?
选项：
A.Coal fuel.
B.Solar power.
C.Wind power generation.
解释：
A is correct.
考点：Tools of regulatory intervention
解析：首先我们根据表格计算一下政府实施政策后，不同发电来源产电的变化
从计算结果看，煤炭发电降低了10.84%，太阳能发电增加了7.67%，风力发电增加了9.43%。因此从环保节能的角度而言，煤炭发电加税政策收到的效果最大。
老师，您好。这道题目为何不像课件例题中进行求解？例如算Coal fuel 中（255/286）^0.25-1?
