Where does most of the nitrogen cycle take place

The us is first  the  u.s. economy  remains the  largest in the world  in terms of nominal  gdp. however, the  u.s. economy  loses its spot as the number one  economy  to china when  measured  in terms of  gdp  based on ppp. in these terms, china's  gdp  is $23.19 trillion exceeds the  u.s. gdp  of $19.42 trillion

As someone who have lived in northern moravia at industrial steel and coal city of ostrava, the closest point is b), but it is questionable. i am not sure how to compare efficiency of largest steel mill in czech republic in comparison to china which is the biggest exporter, but czech steel factories were modernized and run more efficient that 25-35 years ago, and been privatized and owned by mittal. the workforce had been shrinking, so not exactly sure what that c is pointing to (aging of workforce, size of it, or quality). northern moravia is a part of larger coal basin that extend to poland with large coal deposits. this was foundation for the steel industry in the 1800's together with large ore deposits that was mined in proximity of the beskidy mountains less than 25 miles from ostrava. the iron ore mines had been depleted for several decades, and since the late 70's when communists run the country, they were already importing soviet iron ore. coal mining within city of ostrava cased to exist in the 1990's due environmental issues, and also cost. the mines were getting deeper and more costly to operate and there is no more mining within ostrava. couple mines are still in operation in karvina county which is next to ostrava. currently the coal deposits south of the city were not opened due environmental issue which would mean destruction of third largest mountain range in the country. therefore, my conclusion is is b, as the ore and coal resources been shrinking. the biggest challenge not mentioned here is of course competition from russia, ukraine, and china, which can produce steel much cheaper.

the correct answer is - they each vary in size and temperature.

the layers of the earth are not monotone, they are all different, have different sizes and properties.

the four layers are the outer crust, the mantle, the outer core, and the inner core.

the outer crust is solid. it is the top layer, the one we live on, and it is also the smallest and coldest one.

the mantle is lying right bellow the outer crust. it is much bigger, and much hotter, and it is also the layer that influences heavily the upper crust layer with its convection currents.

the outer core is liquid, very hot, relatively big, and it is the third layer (top to bottom).

the inner core is the hottest layers, it is occupying the central part of the planet, and it is the basis on top of all other layers lie on.