Some bats utilize a sound pulse with a rapidly decreasing frequency. A decreasing-frequency pulse has 

A. Decreasing wavelength.

B. Decreasing speed.

C. Increasing wavelength.

D. Increasing speed.

Many species of bats find flying insects by emitting pulses of ultrasound and listening for the reflections. This technique is called echolocation. Bats possess several adaptations that allow them to echolocate very effectively.