My answer was D, the correct is B.
Logic: For 0, both are infinity. Should I learn “one infinity is greater than another infinity”? I ignore this topic in my UG 
You can rewrite the Quantity B as 1 + 1/x, then you are comparing Quantity A(1/x) and Quantity B(1 + 1/x). Thus, Quantity B is greater than A.
You could also subtract 1/x from both sides so that Quantity A becomes 0 and Quantity B becomes 1.
“Infinity” is not a real number, so that’s out of scope for the GRE.