The correct answer is option 4 - trade winds. Trade winds are the planetary winds that blow from the subtropical high-pressure belts towards the Equator. These winds are named as trade winds because they were historically used by sailors for trade routes across the oceans.
Option 1 - westerlies: The westerlies are the planetary winds that blow from the subtropical high-pressure belts towards the mid-latitudes. They are called westerlies because they generally blow from west to east.
Option 2 - doldrums: The doldrums are a region near the Equator where the trade winds from the northern and southern hemispheres converge. They are characterized by low pressure and calm winds, making it difficult for sailing ships to navigate through this area.
Option 3 - polar winds: The polar winds, also known as polar easterlies, are the planetary winds that blow from the polar high-pressure belts towards the mid-latitudes. They are called easterlies because they generally blow from east to west.
Overall, the trade winds are the winds that blow from the subtropical high-pressure belts towards the Equator, making them the correct answer in this case.