Use Random-Variable Notation to Represent the Event $\{ X \leq 4 \}$

Multiple Choice

Use random-variable notation to represent the event.
-Suppose that two balanced dice are rolled. Let X denote the sum of the two numbers. Use random-variable notation to represent the event that the sum of the two numbers is less than 4.

A) $\{ X \leq 4 \}$
B) $\{ X < 4 \}$
C) $\{ X + Y < 4 \}$
D) $( 1,1 ) , ( 1,2 ) , ( 2,1 )$