Why Acrobat continuously calling WININET API?

Don't understand it. When I investigate Acrobat.exe in Process Explorer, I find one of the Acrobat thread is continuously calling WIINET API. Not sure if it is pinging to Update or Some server Server or something else. Although netstat shows no internet connection.

I checked InternetSetStatusCallback API on MSDN. It states the API is used for time intensive network monitoring. 
There are 16-18 threads run in parallel. Surprisingly the i/o activity is high when I load a PDF but no editing is being done.