What is the best title for this list? Grow it: Renewable with Low Profits (Agriculture, Forestry, etc.)
Extract it: Nonrenewable and Selective (Ores, Oil, and Minerals)
Manufacture it: High Value-Added Profits (Mass-Produced Products)

A. Requirement for Success

B. Methods of Gaining National Income

C. Pillage and Plunder

D. Post Industrial Services

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.

2pi more meters because you find the circumference which is 6pi and 4pi and subtract it and you get 2pi

The reason why i feel that the theory of plate tectonics is correct because scientists have found dinosaur bones of the same species in africa, asia, and in the americas. which means that they must have been together at one point in time. plate tectonics is also how the hawaiian islands were formed. as the plate hawaii is on was moving north west, magma would melt through the sea bottom and hardening. forming into the island chain. plate tectonics also explains the mariana trench. two plates were moving away from each other and made a giant crack in the ocean floor running 2,550 kilometers (1,500 miles)  long.

Imma just take a guess and a lunar eclipse.