The correct answer is C: The computed feed point impedance may be incorrect. A disadvantage of decreasing the number of wire segments in an antenna model below 10 segments per half-wavelength is that the computed feed point impedance may be incorrect. Too few segments reduce modeling accuracy. Method of Moments requires sufficient segments to accurately model the current distribution. The general rule is at least 10 segments per half-wavelength for accurate results. With fewer segments, the model can't accurately represent the current distribution, especially near the feed point where current changes rapidly. This leads to incorrect feed point impedance calculations. More segments mean more accurate results but also more computation time. The 10 segments per half-wavelength guideline ensures reasonable accuracy.