This *is* a hard question. Let me give you the short version.
First of all, whenever we use one "as," we need a second "as." You can't say "I'm twice AS fast WHEN COMPARED TO him," right?
So our only choices are A and B, as tongchen said.
Now, "as. . . as" is the same kind of construction as "either. . . or" and "neither. . . nor." (They're all correlative conjunctions.) You guys remember how either/or and neither/nor always need parallel constructions? It's wrong to say "He NEITHER went to the circus NOR to the zoo," because "went to the circus" does not match "to the zoo." You'd have to say, "He went NEITHER to the circus NOR to the zoo."
The same rule applies here.
A is not parallel. What's more, there's no earthly use for "in" in this sentence.
B is parallel. "inhabit Ecuador" matches "inhabit North America."
I could go on and on 'cause it really is a weird question, but I think that's the shortest and simplest explanation.