Question

15.( 2013 湛江) This problem is much more difficult than       .

   A. it   B. one   C. that one   D. that ones

Answer 1

15. C

15. C

句意：这个问题比那个问题要难得多。that one相当于that problem,one在这里替代上文出现的单数可数名词，以避免重复。