Afarmer grows wheat, which she sells to a miller for $90. the miller turns the wheat into flour, which she sells to a baker for $145. the baker turns the wheat into bread, which she sells to consumers for $155. consumers eat the bread. assume that the above transactions account for all economic activity in an economy.

Selling price of wheat by miller= $90 
Selling price of flour by miller= $145 
Selling price of bread by baker = $155 
In this economy the GDP is $155 because it is the final price he got for the wheat.  
So the miller initially had $90 and sold the flour for $145, so he gets an additional 145 - 90 that is $55 gain 
Now the baker have $145 and makes the bread and sell it for $155, so he 155 - 145 that is $10 extra.  
Adding up all these profit amount 90 + 55 + 10 again making it 155 which is GDP.

If you are talking about typical sand you would find at the beach or in a river bed here on earth, there are some differences. i would say the first biggest difference is in composition and mineral make up. although the moon is largely made of the same materials as earth’s mantle and surface, the moon experiences very little weathering (no liquid water and virtually no atmosphere). “earth” sand is typically composed mostly of quartz grains. this is because quartz is highly resistant to both physical and chemical weathering. most of the other minerals originally with the quartz are broken down into fine clay and carried away, chemically eroded/ dissolved, or some combination of the two. this usually leaves only the quartz behind, and so most of the time when you see/think of sand, you are talking about quartz. without these weathering mechanisms on the moon, the “sand” (which is likely more silt or clay sized grains anyways) would consist of mostly other minerals like anorthosite, olivine, and proxene.

: )

The answer is b. a pro-natalist