Question

9. ―Why are you so down,my little boy?

―It has been raining        the whole day. I can't even find an hour to play outside.

   A. off and on   B. on end

   C. once in a while   D. at times

Answer 1

9. B on end意为"连续地"；off and on意为"断断续续地"；once in a while意为"偶尔"；at times意为"有时，不时"。