Step 1: Analyze the range.
We are given \(-1<x<0\). Thus, \(x\) is a negative fraction between \(-1\) and \(0\).
Step 2: Compare \(|x|\) and \(x^2\).
- For example, let \(x = -\tfrac{1}{2}\). Then \(|x| = \tfrac{1}{2}\) and \(x^2 = \tfrac{1}{4}\).
So here \(|x|>x^2\).
- But if \(x = -\tfrac{1}{4}\), then \(|x| = \tfrac{1}{4}\) and \(x^2 = \tfrac{1}{16}\).
Again, \(|x|>x^2\).
Wait — check carefully: actually for all \(-1<x<0\), we have \(|x| = -x\) and since \(|x|<1\), squaring makes it even smaller (\(x^2<|x|\)).
Step 3: Conclusion.
Therefore, \(|x|>x^2\). So Quantity A is greater.
Final Answer:
\[
\boxed{\text{Quantity A is greater.}}
\]