Correct Answer - Option 4 : 20 ∶ 17
Calculations:
Total number of One BHK flats in A, B and C = 20 + 15 + 25 = 60
Total number of two BHK flats in C and D = 25 + 26 = 51
The ratio between One BHK flats in A, B and C to Two BHK flats in C and D = 60 ∶ 51 = 20 ∶ 17
∴ The ratio between One BHK flats in A, B and C to Two BHK flats in C and D is 20 ∶ 17