Answer: Independent variable - brands of bread; dependent variable - how long it takes for mold to form; constant - bread that's not on the counter but in the fridge (or wherever it's supposed to be) instead
Explanation:
The dependent variable is the one that DEPENDS on what will happen. How long it will take for mold to form DEPENDS on the brand of bread.
The thing that is being "depended on" is the independent variable so that would be the brands of the breads.
The constant is the part of the experiment that always stays the same. Here, we aren't really given a constant so we can assume it would be the bread that's in its original position (in the fridge), untouched, so you can compare it with the other experiments (breads on the counter).
Hope this helps!