If 4th december 1999 is Monday then what day is 3rd january 2000 ?

Answer: Option D

Here from 4^th December 1999 to 3^rd January 2000,
there is a difference of 30 days
Number of odd days = $$\frac{30}{7}$$ = 2 odd days
Then no. of odd days = 2 ⇒ tuesday and wednesday (from monday)
Hence on 3^rd january it is wednesday.