Designing Quizzes Designing Master Pages

Question:
What is/are true about master page?

Option A):
All
Option B):
ContentPlaceHolder control can be added only on master page
Option C):
You can add as many ContentPlaceHolders to a Master Page as you need
Option D):
Master page contains a <%@ Master %> directive instead of the normal <%@ Page %> directive

Correct Answer is Option A):
All