If a decline in ownership of all four types of gadgets reflects problems in the economy, which statement can best be
inferred from the chart above? ?
A. The economy was struggling in much of 2009.
B. Economic difficulties were increasing in 2011.
C. Gadget owners escaped any economic difficulty.
D. Economic difficulties started as early as 2006.

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.

I'm pretty sure it's c. extremely gradual but not 100% sure though.

Physical systems is the answer