Answer:
D: 9.75 * 10^6
Explanation:
You can make it easy for yourself if you write both answers in the same form:
(9.4 * 10^6) = (9.4 *10 * 10^5 = 94*10^5) and (3.5 * 10^5) stays the same.
We can now add those numbers up easier:
(94*10^5) + (3.5*10^5) = ( 94 + 3.5 ) * 10^5 = ( 97.5 * 10^5 )
but this answer is not in the option list. We have to perform the same trick as in the beginning, but than the other way around:
(97.5 * 10^5) = (9.75 * 10) * 10^5 = 9.75 * 10^6,
which is exactly option D