请较各位高手位小弟解这题语法

merigo

这题是PPreview里的语法题,请问高手为何答案是"there is more"呢?

14.
Big-band jazz relies on fixed arrangements, where

   _________ than one instrument playing some
of the

   parts,
rather than on improvisation.

              is
more  

              whenever
more  

              there
is more  

              more

蓝衫儿

where后面要加一个完整句，故选there is more