Answer: This is a "CONTROLLED PLACEBO EXPERIMENT".
Explanation: A controlled placebo experiment is a type of research method that is used to check the effectiveness of a drug in a patient. This is done by selecting a sample group, then randomly divide the two group into a placebo group ( this are the group that will receive the drug treatment ) and the controlled group( these are the group that will receive a coloured mixture that looks like the drug, but does not have any effect). Without the groups knowledge about the real drugs and the coloured mixture, but are followed up and tested.
This is a controlled placebo experiment, because 400 student has been choosed as the sample, and are divided into a placebo group and a controlled group, to check the effectiveness of a drug on their memory.
I think we would die because we need the earth atmosphere to live...
The crown of the tooth is covered by<u> the enamel</u>, the hardest substance in the body.
The hardest material in the human body is dental enamel, or the hard tissue that covers the outside of the tooth crown.
It is more mineralized and durable than bone and the most heavily mineralized bodily tissue.
Calcium phosphate, a hard mineral, makes up the majority of it.
Dentin is the layer that lies behind your enamel. It is created from mineral-secreting live cells. The pulp, the primary living component of the tooth, is located underneath the dentin.
Dental crowns are caps that are affixed to broken teeth.
When fillings are ineffective, crowns are utilized to preserve, cover, and restore the contour of your teeth.
Metals, porcelain, resin, and ceramics can all be used to create dental crowns.
To learn more about teeth from given link
brainly.com/question/1378929
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