What is basic rule to create a bundle idetifier in iOS app
<p>I was attempting a online test. there is four option for "What is incorrect bundle id's". Option are - </p>

<pre><code>1) com.companyName.appName
2) com.appName
3) appName
4) com.company-name.app-Name
</code></pre>

<p>I was confused , what will be the correct answer of this question. I have tried to find out, what is basic rule for creating a bundle id. But not got my satisfactory answer. Please help. </p>