How can submit an app to App Review that has two versions: one for iOS and another independent watch appt?

Both apps use the same bundle id (with the watchKit version also having the additional extensions).

I am unclear on which option to use (or whether there's yet another option...):

• Just submit the iOS build and the watchKit version will be included automatically
• Add both builds (iOS and independent watchKit) to the same submission
• Make two separate submissions

Thanks.