matrix – Extract a submatrix

This must be an simple question. Here is my Mathematica code.

A = {{1, 0, 2, -1}, {0, -2, 1, 3}, {2, 1, -1, 0}, {-1, 3, 0, 2}}
K = Inverse[A - x]
T2 = {{a, b}, {c, d}}

Questions:

  1. I would like to extract the submatrix formed by the first two rows and the first two columns of $A$. I tried

    A[[1 ;; 2, 1 ;; 2]

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What is going on?