Enabling Contact to Multiple Accounts allows a single contact to be related to multiple accounts, which can prevent the creation of duplicate contacts with different primary accounts. Duplicate Matching Rules can help identify and prevent duplicate records based on the criteria and actions that you specify.

A multi-cloud integration is a solution that allows connecting and integrating data and applications across different cloud platforms and systems. A multi-cloud integration can provide various benefits, such as scalability, flexibility, resilience, and innovation. To design and implement a robust and scalable multi-cloud integration, a Solution Architect should recommend the following:
* Build an application network by adopting an API-led connectivity approach that packages underlying connectivity and orchestration services as easily discoverable and reusable API building blocks. An application network is a way of organizing applications, data, and devices into a network of reusable services that can be composed and recomposed to meet changing business needs. An API-led connectivity approach is a methodical way to connect data and applications through reusable and purposeful APIs that are developed to play a specific role: unlocking data from systems, composing data into processes, or delivering an experience. By building an application network using an API-led connectivity approach, the Solution Architect can enable a composable, connected, and automated solution that can leverage the capabilities of different cloud platforms and systems in a flexible and agile way.
Option A is incorrect because implementing an integration solution using an outbound messaging design pattern and Salesforce Connect as the integration approach is not suitable or scalable for a multi-cloud integration. An outbound messaging design pattern is a way of sending notifications from Salesforce to external systems when a record is created or updated. Salesforce Connect is a feature that allows accessing and integrating external data from various sources without copying or storing it in Salesforce. These approaches are limited in functionality, performance, security, and reliability for a complex multi-cloud integration scenario. Option B is incorrect because implementing a custom integration solution using lightweight middleware tools like Jitterbit or Talend is not optimal or sustainable for a multi-cloud integration. Lightweight middleware tools are software applications that provide basic integration capabilities, such as data transformation, routing, orchestration, etc. However, these tools are not designed for building an application network or supporting an API-led connectivity approach. They also require custom code or configuration that can increase the cost and complexity of the solution. Option D is incorrect because building multiple point-to-point application integrations connecting the multi-cloud and on-premises applications using SOA (Service-Oriented Architecture) and SOAP web services is not advisable or scalable for a multi-cloud integration. Point-to-point integrations are direct connections between two applications or systems that are tightly coupled and hard to maintain. SOA is an architectural style that organizes applications into loosely coupled services that communicate through standardized interfaces. SOAP web services are protocols that allow exchanging structured data between applications using XML messages. However, these approaches are outdated and inefficient for a modern multi-cloud integration scenario. They also create complexity and fragility in the solution. References:
* https://www.mulesoft.com/resources/api/what-is-api-led-connectivity
* https://www.mulesoft.com/resources/api/what-is-an-application-network
* https://help.salesforce.com/s/articleView?id=sf.datacloud_connect_overview.htm&type=5
* https://help.salesforce.com/s/articleView?id=sf.workflow_om_outboundmessaging.htm&type=5