var data = {
  nagative: [
    ["negative 1 A", "negative 1 B", "negative 1 C"],
    ["negative 2 A", "negative 2 B"],
    ["negative 3 A", "negative 3 B", "negative 3 C", "negative 3 D"],
    ["negative 4 A", "negative 4 B"],
    ["negative 5 A", "negative 5 B", "negative 5 C"]
  ],
  neutral: [
    ["neutral 1 A"],
    ["neutral 2 A", "neutral 2 B", "neutral 2 C"],
    ["neutral 3 A", "neutral 3 B"]
  ],
  posetive: [
    ["posetive 1 A", "posetive 1 B"],
    ["posetive 2 A", "posetive 2 B"],
    ["posetive 3 A", "posetive 3 B"],
    ["posetive 4 A", "posetive 4 B", "posetive 4 C", "posetive 4 D"]
  ]
};

var btn = document.getElementById("btn");

function getRandomItem(obj) {
  return Math.floor(Math.random() * obj.length);
}

function getAnswer(data) {
  var answer = [],
    typeindex = getRandomItem(Object.keys(data)),
    typekey = Object.keys(data)[typeindex],
    sentences = data[typekey];

  sentences.forEach(function(el) {
    var sentenceindex = getRandomItem(el);
    answer.push(el[sentenceindex]);
  });

  return answer.join(". ");
}

btn.addEventListener("click", function(event) {
  var answer = getAnswer(data);
  alert(answer);
});