Final answer:
To overtake another vessel safely, you must alter your course and speed and pass on the side that is safe and clear, avoiding the incorrect and unsafe actions listed in the options.
Step-by-step explanation:
When you wish to overtake another vessel, there are specific maritime rules that must be followed for safety. According to the International Regulations for Preventing Collisions at Sea (COLREGs), when overtaking, you should pass on the side that is safe and clear. This usually means altering your course and speed as necessary to avoid collision and passing at a safe distance. You should not cross directly in front of the other vessel (C), blow your horn continuously (A), or maintain your course and speed (B), as these actions could lead to dangerous situations. Furthermore, it's not always required to pass on the port side (D); it depends on the situation.