Answer:
4
Step-by-step explanation:
In this experiment, there will be a total of four experimental units. This is because there will be two options either baking soda or bleach and each one of these will have two experimental units when combined with either cold or warm water. Therefore, we can create the following units as such...
Baking Soda + Cold Water
Baking Soda + Warm Water
Bleach + Cold Water
Bleach + Warm Water
These would be the 4 total experimental units in this experiment.