chicken eggs hatching paint fading to a lighter color apples ripening on the tree boulders weathering into gravel
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which investigation would require the longest period of observation?
Possibilities:
- chicken eggs hatching
- paint fading to a lighter color
- apples ripening on the tree
- boulders weathering into gravel

boulders weathering into gravel