Answer:
While experimenting researcher can record, test or control the group and while observational study researcher can't do that
Explanation:
An experimental study can be under the control of someone who is doing the research or experiment.
The researcher can also manipulate the experiment and in the observational study, there are no experiments.
The observational study requires the research observing of something, this observing includes what happened in the past, what is saw in the past and what is now.
chiaroscuro
Chiaroscuro means light-dark in
Italian. It is an art method where strong contradiction between light and dark
is used. It showcases effect of contrasted light and shadow made by light
falling unevenly. The technique has already being used by ancient Greek and Roman artists.
The answer is <u><em>BRAIN</em></u> material
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Answer:
Enable the trading of goods and services.