All of the following farmers during the late 19th century except
a. the development of insecticides and germicides.
b. the development of artificial fertilizers.
c. the development of colleges focused on agricultural and mechanical arts.
d. the development of gold backed currency.

The correct option is D.
During the 19th century, the development of artificial fertilizers, insecticides and germicides helped the farmer tremendously by increasing the agricultural yields and thereby increasing their economic status. The development of mechanical machines also made their work easier and faster.