People with Down Syndrome Often Thrust Their Tongues Out as They

People with Down syndrome often thrust their tongues out as they concentrate on a task. Why do they do this?

A) People with Down syndrome usually have small mouths and large tongues, making it difficult to keep the tongue in the mouth.
B) People with Down syndrome like to explore objects with their mouths.
C) People with Down syndrome do not like to work, so they stick out their tongues.
D) People with Down syndrome have low muscle tone and cannot pull their tongues back in their mouths.