The correct option is
C Salivary glands
The buccal cavity is lined by ciliated, columnar epithelium which contains mucus-secreting glands. Mucus lubricates the food. In the frog, salivary glands are absent. The mouth leads into a wide and broad oral or buccal cavity which lies in between the two jaws-the upper and the lower jaw.
So, the correct answer is 'Salivary glands'.