Which of the following is not true of korean maebyeong bottles?

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. 

This is called adduction

Answernon-religious themes became more popular, and people also wanted to show off their wealth because painting was a sign of this at the time;