The answer is letter d. Many examples were found in an artificial cave temple. Mae-byeong (vase) are said to be personalized, meaning, they were made of various materials and qualities so one would be able to own one. Some of these vases are glazed base, some are not (older celadon) to keep it debris free.
Try drinking something heany like milk. The digestive system will require blood to transport any nutrition so blood from elsewhere is directed to it making you sleepy.