After each winter, more pieces of rock break off the cliff. Which of these plays a major role in this process? Dissolving of minerals
Activities of animals
Freezing and thawing of ice
Grass and small plants

Freezing and thawing of ice, when something is ice cold it is easier to break off or apart

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.