Which physical system includes the constantly moving layer of gases, or blanket of air, that surrounds the planet's surface.
a) atmosphere
b) lithosphere
c) hydrosphere
d) biosphere

The atmosphere. It's the layer that is comprised of the early invisble layers of gases that surround a planet. These gases are also described as a "blanket" covering the planet.

A) atmosphere is the physical system that includes constantly moving of gases

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.