EvaCheng

the most obvious effects, and those that would have the largest impact on

people, would be extremes of temperature, precipitation, and storminess.

个人认为and those ... on people 是插入语，and 表示其额外的有巨大影响的effects

，可以理解为补充说明的none-essential modifier; 如果去掉and, those that ....

修饰前面的obvious effects, 成了同位语，改变了语法逻辑

还有B选项错误，并非一个简洁，简洁不简洁只是一个prefer的偏好问题。
真正的语法问题，依我看是：A选项：the most obvious effects would be extremes

of temperature,precipitation, and storminess；B选项：the effects would be

those impacting the most on people——很明显的看到修饰成分变主体，主体内容变

为修饰成分，这种毫无理由的变化，是不合理的。。。。。