What does Google Merchant Center use as the primary way to contact users with important messages, such as feed disapprovals?

 What does Google Merchant Center use as the primary way to contact users with important messages, such as feed disapprovals?

• Messaging in AdWords overview page
• Messaging in Google Merchant Center overview page
• Automated phone messages to account owner
• Email contacts listed in account settings

Answer is – Email contacts listed in account settings