Recall the Application About the Use of Fertilizer and Its

Multiple Choice

Recall the Application about the use of fertilizer and its impact on crop yields to answer the following question(s) . The table is taken from this Application.
Fertilizer and Corn Yield

-According to the Application,the corn production exhibited the principle of diminishing returns because

A) the size of the land and the amount of machinery were held constant.
B) the type of soil was held constant.
C) the type of fertilizer was held constant.
D) the amount of nitrogen in each bag is decreasing.