The use of mechanized farming techniques is well-suited to geographic areas that a. have a shortage of inexpensive labor. b. are closer to major urban areas. c. have large expanses of flat land. d. experience frequent flooding. ea

The use of mechanized farming techniques is well suited to geographic areas that c. have large expanses of flat land. Regions such as the Canadian Prairies is a large expanse of flat land and as such easily supports mechanization in planting crops such as wheat. Mechanization in agriculture would be hampered in areas that experience frequent flooding as equipment could get stuck in mud or suffer other water damage. 

It's probably because some types of violets are blue

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.