TOEFL Listening: ETS-TOEFL听力机经 - LTL5G4643DE29LN1P$

Why does one of the students mention a castle? A. To confirm his understanding of the concept of thermal mass B. To find out whether the buildings' concrete has better thermal properties than stone has C. To suggest that there are alternatives to the design being discussed D. To imply that there could be drawbacks to relying on thermal mass to heat or cool a building