Which of the following is not a factor that has contributed to agricultural success in the us?
a.

expansive infrastructure and mechanized equipment
b.

access to expensive chemical fertilizers and pesticides
c.

controlled population growth
d.

the prohibition of hybridized crops

C. controlled population growth
Controlled population growth has had virtually no effect on farming and is an ideology for the population which is scarcely used in the United States. However, expansive infrastructure and mechanized equipment has kick started mass production of produce, while access to expensive chemical fertilizers and pesticides has helped the United States to grow more quicker and for produce to last longer. The prohibition of hybridized crops has led to a healthier way of farming, such as organic farming which has proved successful and popular in the United States.

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.