The output capacitor, in a power supply filter used to provide power for an SSB or CW transmitter, will give better dynamic regulation if:

SSB and CW transmitters are highly dynamic loads, meaning their current draw changes rapidly in sync with the operator's voice or Morse code keying. To maintain a stable voltage during these rapid current spikes, the power supply must deliver energy instantly. The output capacitor stores electrical charge and acts as a buffer to deliver this instantaneous current. By increasing the output capacitance, the power supply gains a larger energy reservoir, allowing it to easily handle sudden demand peaks without a noticeable drop in output voltage. The other options are either nonsensical, dangerous, or counterproductive. For instance, reversing the polarity of an electrolytic capacitor can cause it to explode, and placing capacitors in series actually decreases the total capacitance.