I want to post a message on google plus business page. Is there any way to do this. I am confused between interactive post, app activities and moment. Should I use Moment to post on business page?
I go through google api site documents, but not getting any solutions. Please let me know if there is any other way to post in google plus page.
It depends on exactly what you mean by "post" and by a "business page".
I'm assuming that the "business page" is one that is not associated with a Google App account. If you're meaning something that will show up on your stream, and that people who have you in a circle will see your post - there is no public API from Google that will do what you want. You need to work with one of their partners, such as HootSuite, to automatically share messages to your stream.
Interactive posts are ways that a visitor to your website can be prompted to share something from your site to their stream on Google+. These interactive posts include both a link to your site as well as an additional "call to action" button to an individual item from your site. It does not automate posts, although it can make some parts of it easier.
App activities and moments are the same thing. They are meant to record actions that take place on your website on Google+, but they do not directly share anything into your stream. Instead, they create an event in your Google+ profile that can be seen only by those you permit it to - you can then, if you wish, share that event to your stream. So while the moment can be generated automatically, it still requires manual action to share it.
Finally, if you have a page that is associated with a Google App account, you can create posts automatically, but those posts are limited in scope. They are only visible to, at most, other people in the same App Domain as the account. This is useful for using Google+ as a communication tool inside an organization, but not useful for communicating with customers, for example.