If 30th December 2024 is a Wednesday, what day would it be on 20th December 2030?

Let's first find the day on 30th December 2030:

That would be 6 years, with only one leap year in between. 

Each leap non-leap year increases the day count by 1 (365, leaving a remainder of 1 when divided by 7)and every leap year increases by 2

The day could increase by 5+2=7 days in total, coming back full circle, giving 30th December 2030 a Wednesday as well. 

Going back 10 days, we would get 20th December 2030 as Sunday. 

Therefore, Option D is the correct answer.