Solution

The word "tranquil" describes a state of calmness and peacefulness, often without disturbance or noise. Therefore, a synonym for "tranquil" would be "peaceful," which also means calm and free from disturbance. Noisy refers to a lot of sound or commotion, which is the opposite of "tranquil." Chaotic describes a state of complete disorder and confusion, which contrasts with the calm nature of "tranquil." Hectic means characterized by intense activity or confusion, which is also the opposite of "tranquil." Thus, "peaceful" is the most appropriate synonym for "tranquil."