Which observation would most likely be made before an experiment? measuring plant growth in response to different fertilizers determining the mass of a product from a chemical reaction counting the number of seeds that germinated after soaking in water noticing the number of tulip plants that sprouted late in a garden

All of these observations seem to be something that one would measure AFTER an experiment and not before. But the best guess here would be that you would only notice the number of tulip plants that sprouted late in a garden and use this information to start and begin/design a new experiment that would be of interest to you.