Answer: Option C
To find the day of the week on 1st January, 1987, we need to know the number of days from 1st January, 1986, to 1st January, 1987. We can then divide the number of days by 7, and the remainder will give us the day of the week on 1st January, 1987.
Explanation:We know that the year 1986 was not a leap year. Therefore, it had 365 days.
Since 1986 was not a leap year, the number of days from 1st January, 1986, to 31st December, 1986, is 365 days.
Now, we need to add 1 day to get to 1st January, 1987.
Thus, the number of days from 1st January, 1986, to 1st January, 1987, is 366.
When we divide 366 by 7, we get a remainder of 2.
Since 1st January, 1986, was a Wednesday, and there are two days left to reach the first Sunday, the 3rd day will be Friday.
Therefore, 1st January, 1987, was a Thursday.
Hence, the correct answer is option C - Thursday.
Formulae Used:

1. Number of days between two dates: (number of years * 365) + number of leap years + (number of days in the remaining year)
2. To check whether a year is a leap year or not:

• If the year is divisible by 4 and not divisible by 100, it is a leap year.
• If the year is divisible by 100, it is not a leap year.
• If the year is divisible by 400, it is a leap year.