The appropriate license type choices for sales and marketing users, given that Salesforce is using delegated authentication, are:

Salesforce license for sales users. This license type allows internalusers, such as employees, to access standard and custom Salesforce objects and features, such as opportunities and reports. This license type also supports delegated authentication, which is a feature that allows Salesforce to delegate the authentication process to an external service by making a SOAP callout to a web service that verifies the user’s credentials. This license type is suitable for sales users who use Salesforce for opportunity management and need to log in with delegated authentication.

Platform license for marketing users. This license type allows internal users to access custom Salesforce objects and features, such as custom apps and tabs. This license type also supports delegated authentication and single sign-on (SSO), which are featuresthat allow users to log in with an external identity provider (IdP) or service provider (SP). This license type is suitable for marketing users who use a third-party application called Nest for lead nurturing and need to log in with SSO using Salesforce asthe IdP or SP.

The other options are not appropriate license types for this scenario. Identity license for sales or marketing users would not allow them to access standard or custom Salesforce objects and features, as this license type only supports identity features, such as SSO and social sign-on. External Identity license for marketing users would not allow them to access custom Salesforce objects and features, as this license type is designed for external users, such as customers or partners, who access a limited set of standard and custom objects in a community. Identity Connect license for marketing users is not a valid license type, as Identity Connect is a desktop application that integrates Salesforce with Microsoft Active Directory (AD) and enables SSO between the two systems. References: [Salesforce Licenses], [Delegated Authentication], [Platform Licenses], [Single Sign-On], [External Identity Licenses], [Identity Connect]