You are meeting another power-driven vessel head-on and sound one short blast as a passing signal. The other vessel answers with two short blasts. What should be your next action?

In a situation where two power-driven vessels are meeting head-on and you sound one short blast intending to pass on the starboard side, the appropriate response from the other vessel is to acknowledge your signal. If they respond with two short blasts, this indicates that they intend to pass you on your port side.

In this scenario, the correct action is to sound the danger signal. This is because the two blasts signify a potential misunderstanding or disagreement about the passing arrangements, indicating that the other vessel is not proceeding as expected. The danger signal is a means of alerting the other vessel that you believe a collision may occur and that an immediate course of action is necessary to prevent an accident.

Changing course to starboard may not be the best choice since it does not address the communication failure indicated by their response. Similarly, if you sound another one short blast, it would not resolve the situation effectively since the other vessel's intentions are unclear. Maintaining your course and speed could potentially lead to a dangerous situation, as it may lead both vessels to be unaware that they might collide due to the different assumptions made about the passage.

Thus, sounding the danger signal is the most prudent action to clarify the situation and keep safety as the priority.