Correct Answer: 41 years

Solution : 8 years ago, the average age of Rahul's family consisting of 6 members was 35 years.
Total of 6 members 8 year ago = 35 × 6 = 210
One year ago a new baby was born in this family.
The total age of 6 members at the time the baby was born = 210 + 6 × 7 = 252
Present age of 6 members and baby = 252 + 7 = 259
The total age of the family after 4 years = 259 + 4 × 7 = 287
So, the average after 4 years = $\frac{\text{Sum of observations}}{\text{Total number of observations}}=\frac{287}{7} = 41$ years
Hence, the correct answer is 41 years.