Final answer:
In duple meter, there are two beats per measure, which is essential for the rhythm and marching timing in many marching band pieces.
Step-by-step explanation:
Duple meter in music means there are two beats per measure. Therefore, the correct answer is A. Two beats per measure. An example of duple meter can be found in many marching band pieces, where you can feel a strong beat followed by a weaker beat, similar to the rhythm of a march. This meter is widespread as it creates a steady and predictable rhythmic pattern that is easy to walk or march to, making it ideal for marching bands.