If 10 October 2003 was a Friday, then what was the day of the week on 8 October 2015?

The correct option is Thursday.

To find the day of the week on 8 October 2015 given that 10 October 2003 was a Friday, we can calculate the total number of odd days between the two dates.

Step 1: Calculate the number of odd days from 10 October 2003 to 10 October 2015.

The total number of years between 10 October 2003 and 10 October 2015 is:
2015 - 2003 = 12 years.

During these 12 years, we need to count the ordinary years and leap years:
- Leap years in this period (years with 29 days in February): 2004, 2008, 2012 (Total = 3 leap years)
- Ordinary years: 12 - 3 = 9 ordinary years.

Each ordinary year contributes 1 odd day and each leap year contributes 2 odd days.
Total odd days from years = (9 × 1) + (3 × 2) = 9 + 6 = 15 odd days.

Dividing 15 by 7 to get the remaining odd days:
15 mod 7 = 1 odd day.

So, 10 October 2015 would be 1 day ahead of 10 October 2003 (Friday + 1 day = Saturday).

Step 2: Find the day of the week on 8 October 2015.

Since 10 October 2015 is a Saturday:
- 9 October 2015 is Friday.
- 8 October 2015 is Thursday.

Therefore, the day of the week on 8 October 2015 was Thursday.