What Salesforce technology best fulfills this requirement?

Universal Containers has a customer setup process that relies on external database to send customers welcome & registration emails. When a customer contacts Universal containers via phone they need to receive the welcome email shortly following the conversation with the UC representative. Universal containers representatives work exclusively in Salesforce and any new customer contacts are created in Salesforce by the representative. The external database exposes a SOAP API for integration with other applications.

What Salesforce technology best fulfills this requirement?
A . Write a nightly batch synchronization to send customer information to the external database.
B . Write an outbound message to send customer Information to an ES
D . Write an outbound message to send customer Information to the external database.
E . Write a trigger with an @future method to send customer Information to the external database

Answer: C