Final answer:
Refractory clay is versatile and used for making firebricks, crucibles, and various objects exposed to high temperatures, so the correct answer is 'All of the above'.
Step-by-step explanation:
Refractory clay is used in various high-temperature applications due to its ability to retain its essential properties at such temperatures. This type of clay is used for making firebricks, which are integral to lining high-temperature furnaces. It's also used for making crucibles, which are containers that can withstand extreme heat and are used for melting and refining metals. Additionally, refractory clay is used for creating objects exposed to high temperatures, encompassing applications such as furnace tubes, lighting tubes, and the manufacture of fiberglass for reinforced plastics and other high-heat resistant materials. Hence, the answer to the student's question would be 4) All of the above.