The term "castle-in-the-air" is actually a term that means something that is imaginary and extravagant and most likely are not realized or carried out. In other words, this is similar to the term "daydream". When we use TV as <span>"castle-in-the-air", the danger for this is that people tend to view something as a reality instead of just accepting it as fantasy. Hope this helps.</span>
Answer:
a series of recent post by astronauts.
Explanation:
this would be the most reliable source because it is first hand information, instead of people who havent visited space or traveled space.
The correct option is D.
Marginal cost refers to the amount of money it cost a company to produce one more of a particular product while the marginal benefit refers to the benefit that is obtained as a result of producing that one extra product. Profit is maximized when the marginal cost equals the marginal benefits.
