Correct Answer: Monday

Solution : Given:
9 July 1978 is a Sunday.

Let's calculate the total number of days from the 9th of July 1978 to the 19th of September 1983 –

Number of days from 9 July 1978 to 31 December 1978 = 22 + 31 + 30 + 31 + 30 + 31 = 175
Number of days from 1 January 1979 to 31 December 1982 = (4 × 365) + 1 = 1461 (1 leap year)
Number of days from 1 January 1983 to 19 September 1983 = 31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 19 = 262
So, the total number of days from 9 July 1978 to 9 September 1983 = 175 + 1461 + 262 = 1898
Now, on dividing 1898 by 7, we get 271 as the quotient and 1 as the remainder.

Therefore, add 1 to Sunday, Sunday + 1 = Monday

So, the 9th of September 1983 will be Monday. Hence, the first option is correct.