Final answer:
The antonym for turbulent is tranquil.
Step-by-step explanation:
A) Tranquil
B) Tempestuous
C) Horrid
D) Concealed
The antonym for turbulent is tranquil. When something is turbulent, it is characterized by chaos, disorder, or unrest. On the other hand, when something is tranquil it is calm, peaceful, and serene.