I'm sure that it is the US had abundant natural resources.
I believe it's A.
The Muslims did control Jerusalem for a time, and I believe that they forced the Christians out of it.
Also the Crusaders did sack Constantinople when they were not allowed in by the government there.
I don't know what D is but I'll assume that it is true because I think A is false.
B. The actual number of farmers increased between 1840 and 1900.
D I think since there are children in a factory :)