How to get the value of a 2 word key in a JSON string?

Question

Since a long time, I'm struggling to solve this:

         var obj = {
            Goa: "A",
            Assam: "B",
            "Arunachal Pradesh":"C"
                 }

        alert(obj."Goa")  // Alerts A
        alert(obj."Assam")  // Alerts B
        alert(obj."Arunachal Pradesh")  // But no Alerts

How can I get the alert for the key term Arunachal Pradesh which have 2 words with space between them?