The sum of the digits of the integer equal to $777777777777777^{2}-222222222222223^{2}$ is
(A) 148
(B) 84
(C) 74
(D) 69
(E) 79
Let $x=777777777777777$ and $y=222222222222223$.

So the required quantity is $x^{2}-y^{2}=(x+y)(x-y)$.

Now $x+y=1000000000000000$ and $x-y=555555555555554$.

Thus, $x^{2}-y^{2}=555555555555554000000000000000$, ie. the sum of the digits is $14 \times 5+4=74$.

ANSWER: (C)