Answer: Third option is correct.
Explanation:
Since we have given by
Event A: the red die shows 1
Event B : the numbers add to 4
Event C: at least one of the numbers is 3
Event D : the numbers do not add to 9.
D' means the number add to 9.
We need to write the following statement in symbolic form:
Either the numbers add to 9 or the red die shows a 1.
So, it becomes,

Number of elements in D'∪A = 1.
Hence, Third option is correct.