这个MR不是从3000就已经开始下降了吗？

问题如下：

In order to improve the yield of his corn crop, a farmer has subdivided his acreage this year and has experimented with different amounts of water per acre. The results of his study are shown in the following table

The point (in gallons of water per acre) where the effect of diminishing returns is first observed is closest to:

选项：

A.3,000.00 B.3,150.00 C.3,300.00

解释：

Solution

B is correct. The yield per gallon, shown in the following table, peaks at 3,000 gallons and starts to decline above that—that is, at 3,150.

A is incorrect. It is the volume of maximum efficiency based on yield per acre.

C is incorrect. It is where there is the largest decrease in yield in bushels per acre but is not the first point of diminishing returns per gallon of water.