Answer:
Because it was sand in the seawater sample
Explanation:
By the evaporation method you put the seawater in a boiler so that all the water evaporates from the jar, after that, as the salt is a heaver compound it doesn't evaporates and because of this you can weight the amount of salt that is left. If in the initial sample you also have sand this weight will interfier with the amount of salt that is cuantified when you weight it and because of this the salinity results will be incorrect.
C, because most underdeveloped countries have poor infrastructure largely due to war and corruption.
B. He felt that without the bomb, a costly invasion would be necessary, and many Americans who fought were already tired island-hopping.