The correct answer is: C. Both
Material trains can work during both day and night. In fact, they often work during the night when there is less traffic on the roads. This allows them to move materials more quickly and efficiently.
Option A: Day. Material trains can work during the day. This is the most common time for material trains to operate. They can move materials to and from construction sites, factories, and other businesses.
Option B: Night. Material trains can also work during the night. This is often the best time for them to move materials because there is less traffic on the roads. This allows them to move materials more quickly and efficiently.
Option D: None of these. Material trains can work during both day and night.