What is the recommended procedure for an Administrator to add new dynamic attribute to a Notification Template?

What is the recommended procedure for an Administrator to add new dynamic attribute to a Notification Template?
A . Add a new Syntax Tag to the Notification Syntax ID
B. Copy and paste a Syntax Tag from any other template
C. Add a new Syntax Tag to the Notification Template
D. Select an existing Syntax Tag from a list

Answer: D