Explanation:

Correct option 2: 6 

Given 

12 men can complete a painting work in 8 days.

So, total work in term of Man's days = 96.

and One day work of a man = 1/96

Similarly,

16 women can complete the same painting work in 12 days.

One day work of a woman = 1/16x12=1/192

Now we compare one day work of a man with one day work of a Woman.

1/96 : 1/192

1.e. 2:1

=> 1 man = 2 Women.

Now,  8 men started painting the house. After 6 days of painting 2 men were replaced by 4 women. 

8 men's 6 days work = 48 units

Remaining work = 96- 48 = 48 units.

After 6 days 2 Men replaced with 4 women.  

Now we have 4 Men + 4 Women

=> 6 Men + 2 Men ( because 4 women are equal to 2 Men)

=> 8 Men

Now, time required to complete the pending work = .48/8= 6 days