Superior manpower, industry, access to trade, finances, leadership, and more.
Answer:
The poorer areas of the cities were characterised by overcrowded, badly built, unsanitary living accommodation, and filthy streets. Cholera, carried by dirty water, killed 16,000 Londoners in 1849 alone, and smallpox, scarlet fever, typhus, scurvy and rickets were rife.
Once the Spanish settled in the Caribbean they quickly began importing slaves from Africa to work in the sugar mills. Sugar was in incredibly high demand in Europe at the time.
Hm, this is not an easy question.
Generally the best way to prevent a nuclear disaster is not to have any weapons, so A would be a good option. But in the modern world, complete destruction of all weapons is not feasible, and people believe that since US and Russia limited their number of weapons, this is no longer such a big concern (option D, which is I think the best. Personally, however I faviour A as a solution to the problem of nuclear weapons).