Numpy select elements with a condition along axis

Question

I have a 2D numpy array x as:

[  [ 1,  2,  3],
   [ 4,  5,  6],
   [ 7,  8,  9],
   [10, 11, 12],
   [13, 14, 15],
   [16, 17, 18],
   [19, 20, 21],
   [22, 2