The given problem:
The problem states that if 16th December, 2008 was a Monday, then what day of the week would be on 16th December, 2007?

Approach:
To solve this problem, we need to understand the concept of leap years and the number of days in a year.

Leap Years:
A leap year is a year that is exactly divisible by 4, except for years that are divisible by 100. However, years that are divisible by 400 are leap years. For example, 2000 and 2004 were leap years, whereas 1900 was not.

Number of days in a year:
A non-leap year has 365 days, and a leap year has 366 days.

Calculating the number of days between 16th December, 2007 and 16th December, 2008:
To find the number of days between two dates, we need to consider the number of days in each month and the number of leap years.

In this case, we have:
- 16 days in December 2007
- 31 days in January 2008
- 29 days in February 2008 (leap year)
- 31 days in March 2008
- 30 days in April 2008
- 31 days in May 2008
- 30 days in June 2008
- 31 days in July 2008
- 31 days in August 2008
- 30 days in September 2008
- 31 days in October 2008
- 30 days in November 2008
- 16 days in December 2008

Adding all these days, we get a total of 366 days.

Calculating the day of the week:
To calculate the day of the week, we need to divide the total number of days by 7 (the number of days in a week) and find the remainder.

In this case, 366 divided by 7 gives a remainder of 2.

Since 16th December, 2008 was a Monday and there is a remainder of 2, we need to go back 2 days from Monday. Hence, the day on 16th December, 2007 would be Saturday.

Therefore, the correct answer is option A) Saturday.