Explanation: The minimum range of a RADAR system is determined by the transmitted pulse width because, during the time the RADAR is actively transmitting a pulse, its own receiver is effectively "blinded" or unable to detect incoming echoes. For a target to be detected, the transmitted pulse must entirely finish, and the echo from the target must return *after* the transmitter has ceased its emission and the receiver is active again. If a target is too close, its echo would return while the RADAR is still transmitting the initial pulse, or during the very short period immediately following transmission when the receiver might still be recovering. A shorter transmitted pulse width means this "blind time" is shorter, allowing the RADAR to detect echoes from closer targets. Options B and D (Pulse Repetition Rate/Frequency) primarily determine the *maximum* unambiguous range, not the minimum. If the PRF is too high, echoes from distant targets might arrive after the next pulse has been transmitted, leading to ambiguous range readings. Option A (Frequency) influences factors like resolution, atmospheric absorption, and antenna size, but not the fundamental minimum detection range tied to the system's "dead time" during transmission.