Question

 As       rule, apples are sold by      weight and eggs by       dozen.

  A. a; 不填；the          B. a; the; the

  C. a; a; the               D. the; 不填；不填

Answer 1

選A。as a rule(通常地)是固定詞組；在度量名詞前，表示付工資、賣、租等方式時，用the, 如paid by the hour (day, moth, piece…), sold by the yard (dozen, ton…)，比較by weight (按重量)。