The vegetables grown in this district are much better than in that district.A. /B. thatC.

问题补充：

The vegetables grown in this district are much better than in that district.

A. /

B. that

C. ones

D. those

答案：

A. /

B. that

C. ones

(答案→)D. those

解析：考察指示代词用法，根据题意这个地区的蔬菜比那个地区的蔬菜生长的好的多。前文蔬菜为复数形式，可知下文的比较对象也是复数形式，ones指任何一个，故选D，那些。