Well, it could be a problem of all of those, honestly. Even acid rain that develops in one country can go over to another due to the winds and cause problems there.
However, any urban area at this point in time, where there are many people and many gases being produced, will create acid rain, so D is likely to be the answer.
Explanation:
Gunpowder, also known as the retronym black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur (S), carbon (C), and potassium nitrate (saltpeter, KNO3). The sulfur and charcoal act as fuels while the saltpeter is an oxidizer.[1][2] Gunpowder has been widely used as a propellant in firearms, artillery, rocketry, and pyrotechnics, including use as a blasting agent for explosives in quarrying, mining, and road building.
Black powder for muzzleloading firearms and in granulation size. U.S. quarter (diameter of .955 inch (24.26 mm)) for comparison.
Gunpowder was invented in 9th-century China as one of the Four Great Inventions, and spread throughout most parts of Eurasia by the end of the 13th century.[3] Originally developed by the Taoists for medicinal purposes, gunpowder was first used for warfare around 904 AD.[4]
Gunpowder is classified as a low explosive because of its relatively slow decomposition rate and consequently low brisance. Low explosives deflagrate (i.e., burn) at subsonic speeds, whereas high explosives detonate producing a supersonic shockwave. Ignition of gunpowder packed behind a projectile generates enough pressure to force the shot from the muzzle at high speed, but usually not enough force to rupture the gun barrel. Gunpowder thus makes a good propellant, but is less suitable for shattering rock or fortifications with its low-yield explosive power. Nonetheless it was widely used to fill fused artillery shells (and used in mining and civil engineering projects) until the second half of the 19th century, when the first high explosives were put into use.
Gunpowder is no longer used in modern weapons, nor is it used for industrial purposes, due to its relative inefficiency compared to newer alternatives such as dynamite and ammonium nitrate/fuel oil.[5][6] Today gunpowder firearms are limited primarily to hunting, target shooting, and bulletless historical reenactments.
I honestly believe to help your wellbeing that ,Under a block grant, proponents argued, states could shift the funds freed up when families left welfare for work to child care or other work supports, where need would increase. States also could invest more in work programs to reflect the increased emphasis on welfare as temporary and work-focused.
