Choose the correct word to complete the royal advisor's warning.

"The dragon is currently asleep and peaceful, but it will only remain _____ if you stop playing those dreadful bagpipes!"

The correct answer is so.

The word so can act as a substitute for an adjective or an adjective phrase functioning as a subject complement (in this case, "asleep and peaceful"). It frequently follows linking verbs like remain, seem, appear, and become.

Such is generally used to substitute for noun phrases, not adjective phrases, making "remain such" incorrect in this context.