From the question, we have the following:
1/5 before lunch
3/7 after lunch
Before : After
(1/5 : 3/7) = 7/35 : 15/35
Therefore,
After lunch - Before lunch:
= 15/35 - 7/35
= 8/35
Therefore, what was uploaded after lunch was 8/35 more than before lunch.
So, the correct option is C, which is 8/35.