Correct Option (D)
The problem provides a reference point: 5th November is a Thursday.
To determine the day of the week for 20th December, the total number of days between 5th November and 20th December must be calculated:
- Number of days remaining in November from 5th November: 30 − 5 = 25 days.
- Number of days in December up to 20th December: 20 days.
- Total number of days = 25 (November) + 20 (December) = 45 days.
Next, the number of odd days is determined by dividing the total days by 7:
- Number of odd days = 45 ÷ 7 = 6 weeks and 3 odd days.
Since 5th November is a Thursday, the day for 20th December will be 3 days after Thursday:
- Thursday + 1 day = Friday
- Thursday + 2 days = Saturday
- Thursday + 3 days = Sunday
Therefore, 20th December is a Sunday.
Incorrect Options:
Options (A) Monday, (B) Thursday, and (C) Saturday are incorrect. The calculation based on the given reference point of 5th November being a Thursday leads to 20th December being a Sunday, not any of the other specified days.