问题如下：
Price elasticity of demand for a good will most likely be greater if:
选项：
A.there are no substitutes for the good.
B.consumers consider the good as discretionary.
C.consumers spend a small portion of their budget on the good.
解释：
B is correct.
Price elasticity of demand is likely to be greater for items that are seen as optional or discretionary.
考点：影响需求价格弹性的因素。
解析：
影响需求价格弹性的因素有四点：
Availability of substitutes指替代品容易获取程度，商品容易获取弹性大，不容易获取则弹性小。
Relative amount of income spent on the good 商品花费占收入比。比重大弹性大。比如买房子。
Time since the price change.商品价格变化后的时间，价格改变后时间越长，消费者的机动性越大，弹性越大。
Whether the good or service is seen to be discretionary or non-discretionary商品是否是必须需要的。如果消费可以砍掉，那么弹性就比较大。B选项正确
选项B，如果是必需品的话，弹性不应该是更小吗，怎么会greater呢？
