Answer:
D
A- If you were to add 8.313213.... and 7.123123.... it will not be rational.
B- If you were to add 6 and 2.3424... it will not be rational.
C- If you added 3.15 and 2.15 it will be rational.
D- If you multiplied 3.14 and 4.15 it will be rational.