The correct answer is C) cold front has passed. In the Northern Hemisphere, winds veering sharply to the west or northwest with increasing speed indicate the passage of a cold front. As a cold front moves through, the wind shifts to the west or northwest and increases in speed as the colder, denser air mass pushes out the warmer, less dense air. The other options are incorrect because: A) a high pressure center passing would typically bring calmer winds, not increasing speeds, B) a low pressure center approaching would typically bring winds shifting to the south or southeast, and D) a stationary front would not necessarily cause a sharp shift in wind direction and speed.