Mandarin Chinese has all of the following contrasting tones except:​

A) ​flat
B) ​rising
C) ​falling
D) ​whistling

Contrasting Tones

Employing distinctly different pitches, colors, or attitudes in speech, writing, art, or music to highlight differences or create effects.

Whistling

Producing a high-pitched sound by forcing air through a small hole formed by the lips, teeth, or objects, often used as a form of communication or musical expression.