Final answer:
The audience was impressed by the singer's ability to hit the high and low notes, showcasing the singer's vocal range.
Step-by-step explanation:
The statement that the audience was impressed by the singer's ability to hit the high and low notes refers to the singer's vocal range. Vocal range is the span from the lowest to the highest note a singer can produce. It showcases the singer's ability to effortlessly transition between different pitches. A wide vocal range is often considered a sign of skill and talent in singing.