20. After heating a metal annular disc with inner radius r and outer radius r0 (see Fig. 5), which of the following statements is not true? 
(A) The outer radius r0 increases.
(B) The inner radius rĄ increases.
(C) The total area of the annular disc increases.
(D) The width w, where w =
, of the annular disc remains the same.
(E) The sum of the areas of the annular disc and the hole increases.
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統計: 尚無統計資料
統計: 尚無統計資料