The fourth alternative is correct (D).
Currently, many different tools provide the data that is used to detect natural disasters such as storms and hurricanes. These tools generate information that is used for forecasting and for issuing alerts and warnings.
One of these very commonly used tools is Radar. In the US, hurricanes are very common in coastal regions. Therefore, the country has developed a radar system that covers the Gulf of Mexico and the coastal regions of the Atlantic. The details revealed by the radar help to perfect the hurricane alerts as the storms approach the earth.
