Answer:
 Option (D) 16.57%
Step-by-step explanation:
Data provided in the question:
Realized gain 
r₁ = 20%
r₂ = 20%
r₃ = 10%
Now,
Geometric average = 
![[(1+r_1)*(1+r_2)*...*(1+r_n)]^{(1)/(n)}](https://img.qammunity.org/2020/formulas/business/college/97gt939h6h9kedabv30nnykk2as4wfy1y7.png) - 1
 - 1
here,
n = 3 
therefore,
Geometric average = 
![[(1+0.20)*(1+0.20)*(1+0.10)]^{(1)/(3)}](https://img.qammunity.org/2020/formulas/business/college/uk4lz5abdfgzbsisml2vyttvhc2ptenj1n.png) - 1
 - 1
or
Geometric average = 
![[1.584]^{(1)/(3)}](https://img.qammunity.org/2020/formulas/business/college/eq16mltogvk5e5urg3yln2pefwtpw4r5se.png) - 1
 - 1
or
Geometric average = 1.1657 - 1
or
Geometric average = 0.1657 
= 0.1657 × 100%
= 16.57%