If artisans don't wrap the final product of Cốm Làng Vòng in two layers of leaves, they ______ preserve its fragrance before selling it to customers.

Mark the letter A, B, C, or D on your answer sheet to indicate the word which best completes each of the following sentences.

If artisans don't wrap the final product of Cốm Làng Vòng in two layers of leaves, they ______ preserve its fragrance before selling it to customers.