Explanation: The VHF marine band operates primarily between 156 and 162 MHz. A common and efficient design for a temporary vertical antenna is a quarter-wave monopole. To calculate the approximate physical length of a quarter-wave antenna in feet, we use the formula: Length (feet) = 234 / Frequency (MHz) Using an approximate center frequency of 159 MHz for the marine band: Length = 234 / 159 MHz ≈ 1.47 feet To convert this to inches: 1.47 feet * 12 inches/foot ≈ 17.64 inches Therefore, an 18-inch antenna is the closest approximation to a quarter-wavelength for the VHF marine band. Options A, B, and C are significantly shorter than the resonant quarter-wave length, which would lead to very poor antenna efficiency and high Standing Wave Ratio (SWR).