jquery – Get nested JSON keys only

Example JSON

{
  "one": [{
    "A": {"name":"example"},
    "B": {}
  }],
  "two": [{
    "A": {"name":"booger"},
    "B": {}
  }]
}

Using this I can get keys “one” and “two” to be listed.

$.getJSON('blahblah.js', function(data){
  $.each(data, function(key){
    console.log(key);
  });
});

But using this, I can’t get “A” and “B” to be listed.

$.getJSON('blahblah.js', function(data){
  $.each(data.one, function(key){
    console.log(key);
  });
});

Why not? And how do I get those inner keys(is this the correct term?) to be listed.
Thanks