Question

Bats use ultrasound in echolocation. This sound is characterized by __low frequencylow amplitudehigh frequencyhigh amplitude

Answer 1

Both use reflected sound waves.

Answer 2

Bats use high frequency. Whenever somebody says a quantity is "high",
you have to ask "compared to what ?". In this case, it's compared to human
hearing ... we can't hear bats at all, or if we can, it just sounds like a 'click'.