Question

If a girl is standing in front of a smooth surface from which a sound is reflected, the girl may hear

Answer 1

D. Two similar sets of sounds if she is also near the source of the sound. 

Just took the test, got it right! =]

Answer 2

The correct answer is option D.

If a girl is standing in front of a smooth surface from which a sound is reflected, the girl may hear two similar sets of sounds if she is also near the source of the sound.

For proper reflection of all sorts of energy waves, a hard flat surface is preferable. This helps to reflect waves without losing energy. Hard and smooth surfaces are best for travelling of sound waves because sound is related to pressure.