The correct answer is A) check operating pressures and temperatures, and check for leaks. After starting an engine, it is important to monitor the operating pressures and temperatures to ensure the engine is functioning properly and to detect any potential issues. Checking for leaks is also crucial to identify and address any problems that could lead to further damage or safety hazards. This is a standard procedure recommended by engine manufacturers and required by regulations for safe and responsible engine operation. The other options are incorrect because: B) paying no attention unless there are unusual noises is not a recommended practice, as it could lead to undetected issues; C) increasing engine speed immediately is not advisable, as the engine needs time to properly circulate oil and reach operating temperature; and D) running the engine at idle until the temperature increases is not sufficient, as you should also check pressures and look for leaks.