Answer:
food, water, transportation, bathing
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Explanation:
A city that has a problem with smog is most likely a MDC and is experiencing it due to heavy air pollution. <span />
A radioactive element with a half-life of 1,000 years, and starting mass of 20 grams, will need 2,000 years to decrease to 5 grams.
Explanation:
The radioactive elements all have a specific half-life. Each element's half-life is well known, and they are used by scientists of numerous fields as they are excellent for determining the age of a particular item, be it or organic or non-organic nature. In this case, we have a radioactive element with a half-life of 1,000 years, and starting mass of 20 grams.
The half-life basically means that half of the mass of an element is lost during a particular period of time. For the element in question we need to find out how much time will be needed for it to decrease to 5 grams. In order to get to the result, we just need to add 1,000 years on every decrease of half of the mass:
20/2 = 10
10/2 = 5
So in 1,000 years, the element in question will decrease to 10 grams, and in further 1,000 years (2,000 cumulatively) it will decrease to 5 grams.
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Answer:
The correct answer is: b. intermediate- to low-mass stars (between 0.8x to 8x the mass of our Sun).
Explanation:
Once the hydrogen in the nucleus is finished, the hydrostatic equilibrium is broken, and gravity is able to overcome radiation. This causes the star's core to contract, thus increasing its internal temperature and density. Meanwhile, due to convection, the outer layers expand, so the external temperature decreases. The star increases its external size becoming what we know as the Red Giant.
By increasing the temperature in the core, the necessary conditions are given to begin to fuse Helium and convert it into Carbon. So the core is getting denser and the outer layers of the star expand even more.
The end of our star is marked by the moment when the helium in the nucleus ends. In addition, the outer layers are so far apart that they no longer exert sufficient pressure to compress the core and trigger carbon fusion. In parallel, the star is so large that the outer layers of the star escape the gravity of the star, pushed by radiation. In this way, the interstellar medium of helium, carbon and a little oxygen is enriched. Leaving behind a White Dwarf, the nucleus of the star in which Helium has become Carbon.
