-  Let son's age 8 years ago be x years. Then, Rohit's age 8 years ago = 4x years.
            
   Son's age after 8 years = (x + 8) + 8 = (x + 16) years.
            
   Rohit's age after 8 years = (4x + 8) + 8 = (4x+ 16) years.
            
   2 (x + 16) = 4x + 16
           
   2x = 16
     x = 8.
      
  Hence, son's 'present age = (x + 8) = 16 years.
  Rohit'spresent age = (4x + 8) = 40 years.

Let the present age of Rohit be "R" and his son be "S".

According to the problem statement, we can form two equations:

Equation 1: R - 8 = 4(S - 8) (Rohit was 4 times as old as his son 8 years ago)

Equation 2: R + 8 = 2(S + 8) (After 8 years, Rohit will be twice as old as his son)

We need to solve these two equations to find the present ages of Rohit and his son.

Solving Equation 1 for R, we get:

R - 8 = 4S - 32

R = 4S - 24

Substituting this value of R in Equation 2, we get:

4S - 24 + 8 = 2S + 16

Simplifying this equation, we get:

2S = 32

S = 16

So, the present age of Rohit's son is 16 years.

Substituting this value of S in Equation 1, we get:

R - 8 = 4(16 - 8)

R - 8 = 32

R = 40

So, the present age of Rohit is 40 years.

Therefore, Option D (40 years) is the correct answer.

Some important formulas that we have used in this problem are:

If a person's present age is "P", and "N" years ago their age was "A", then we can write: P = A + N

If a person's present age is "P", and "N" years from now their age will be "B", then we can write: B = P + N

If two people's ages are "A" and "B", and one person is "X" times as old as the other, then we can write: A = X * B

If you think the solution is wrong then please provide your own solution below in the comments section .