Answer:
monopolistic competition is when an industry has many firms offering products that are similar but not identical. unlike a monopoly, these firms have little power to set curtail supply or raise prices to increase profit. Monopolies dictate over a specific thing so they are the only thing that is selling.
Explanation:
google & known knowledge
Answer:
The correct answer is Introspection
Explanation:
From the given question, from the history of psychology, we can asses Dave's claim using what is called Introspection
Introspection refers to the training of participants to report elements of specific sensory experiences.
Introspection is also the scrutiny of one's personal feelings and conscious thoughts. In psychology, the process of introspection deals with exclusively on observation of one's mental state, while in the context of spirituality it may be called the examination of one's soul.
The lowest volume level that a person could detect
Density is mass per volume 
With data: 
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Hope this helps.
