Answer:
Marginal analysis is helpful to individuals and businesses in balancing the costs and benefits of additional actions, like whether to produce more, consume more, and similar other decisions, thus determining whether the benefits will exceed costs and increase utility.
Explanation:
Sealed combustion heaters are much safer to operate than other types of space heaters, and operate more efficiently because they do not draw in the heated air from the room and exhaust it to the outdoors. They are also less likely to backdraft and adversely affect indoor air quality.
Less expensive (and less efficient) units use the room air for combustion. They do not have a sealed glass front to keep room air away from the fire and should not be confused with a sealed combustion heater.
1 and 3 are correct, this is due to the fact that modern technology is constantly growing and other developed nations are feeling threatened or inferior when another developed nation grows further ahead. National security has also grown global, just the threat of a foreign country developing nuclear capability is enough for another country to launch missle strikes or other acts in order to quell the threat of another nuclear capable country. 2 is not correct because industrial strategies are being shared throughout the world constantly and the safety of a country no longer stands by their standing army or navy, but by the threat of nuclear capability or a possibility of retaliation through explosive nature. Even today, most wars are done through the army holding down a line, and the navy/airforce launching long ranged missile attacks of various nature.