To annualize the return over a 16-month period, the correct approach involves using the formula for annualized returns:

$T_{\text{annual}} = (1 + T_{\text{period}})^c - 1$

where $c$ is the number of periods in a year. For 16 months, $c = \frac{12}{16} = 0.75$. Substituting the given return of 13.1% (0.13100):

$(1 + 0.13100)^{0.75} - 1 = 1.09672 - 1 = 0.09672 \text{ or } 9.7\%$

Option A (9.3%) is incorrect as it represents the monthly compound return annualized by multiplying by 12. Option C (9.8%) is incorrect as it uses the arithmetic mean return, which is not appropriate for annualizing compound returns.