A: In a lab a scientist measures the height of roses that received different fertilizers.
An experiment must include variables. The other three are just measurements, but since the scientist is varying the types of fertilizers used, this better describes an experiment. It is also done in a controlled environment (in a lab) which helps to eliminate other uncertainties.
This is true. They are structured to keep well in cold environments so sticking them places such as the refrigerator keeps the well conserved for some time.
