Digital Engagement is a set of features in Service Cloud that enables agents to communicate with customers using social messaging channels such as Facebook, WhatsApp, and SMS. To justify the recommendation of implementing Digital Engagement, a Solution Architect can use the following reasons:

Mobile Connect lacks integration with the service agent console without Digital Engagement. Mobile Connect is a feature in Marketing Cloud that allows sending and receiving SMS messages. However, without Digital Engagement, Mobile Connect messages cannot be handled by Service Cloud agents in the service console or omnichannel routing.

Social Studio does not support 1:1 messaging on the apps listed in the scenario. Social Studio is a feature in Marketing Cloud that allows listening and engaging with customers on social media platforms. However, Social Studio does not support direct messaging on Facebook or WhatsApp, which are popular social messaging channels.

Option B is incorrect because Mobile Connect supports outbound messaging in more than 200 countries. Option D is incorrect because Social Studio can respond to public posts or comments on social media platforms. References:

https://help.salesforce.com/s/articleView?id=sf.service_digital_overview.htm &type=5

https://help.salesforce.com/s/articleView?id=sf.mc_moc_mobileconnect.htm &type=5

https://help.salesforce.com/s/articleView?id=sf.mc_moc_supported_countries.htm &type=5

https://help.salesforce.com/s/articleView?id=sf.mc_ss_social_studio_overview.htm &type=5