Final answer:
Weather conditions can affect the audibility of a siren for motorists.
Step-by-step explanation:
The correct answer is c. Weather conditions.
Due to weather conditions, such as heavy rain or strong wind, the sound of a siren can be muffled or distorted. This can make it difficult for motorists to hear the siren until it is too late, especially if they are driving at high speeds or on certain types of roadways.