The third choice is the answer.
This is because chemical change occurs when the (for a lack of better wording) interior of the object is changed in the second one the bread is being broken down chemically by the stomach acid this is because the acid is breaking down the formation of the bread dissolving it and chainring it into something else.
In the 4th one the change that is seen is chemical because the formation of the roof is change the physical appearance may be the same (ie. The size & shape) but their are other changes in the color, texture and maybe taste ( don’t taste a rusting roof lol) these are ways in which you can figure out if a change is chemical or physical.
Physical change occurs when the size and/or shape of an object is changed.
Chemical change occurs when the texture, taste and/or color of the object is changed, but-sometimes chemical change cannot be seen.
Hope this helped :)