Question

Dr. Bennett does an experiment that leads him to invent a machine that can turn salt water into fresh water. It is very slow and costly. He continues his research to improve on his original invention and finds a way to make it work more quickly and inexpensively.

Which of the following ideas does this illustrate?
Scientific research can be based on the results of previous experiments.

Scientific research is only useful for inventing machines.

Scientific research is always expensive and pointless.

Scientific research is never based on the results of previous experiments.