当总效用达到最大值时，边际效用是（ ）。

(单选题)假设王五的消费决策遵循费雪两期模型，王五在第一期的收入为1000元，第二期的收入为3100元，他可以按市场利率借贷或储蓄 (单选题)如果无差异曲线相交，那么（ ）。 (单选题)Mathew Brady（ ）. (单选题)If a photographer wanted to take pictures of moving things i (单选题)The Daguerreotype was（ ）. (单选题)The first photo taken by Niepce was a picture of（ ）. (单选题)How much should a couple with one child at 10 and another at (单选题)If we book a trip online, we have the following benefits EXC (单选题)What do we know about Dickens in this passage? (单选题)During the visit, visitors can（ ）.