OG2018 SC 241答案的解释

有很多可能的L

Analysts blamed May's sluggish retail sales on unexciting merchandise as well as the weather, colder and wetter than was usual in some regions, which slowed sales of barbecue grills and lawn furniture

• A
  
  colder and wetter than was usual in some regions, which slowed
  
  
  
• B
  
  which was colder and wetter than usual in some regions,slowing
  
  
  
• C
  
  since it was colder and wetter than usually in some regions,which slowed
  
  
  
• D
  
  being colder and wetter than usually in some regions,slowing
  
  
  
• E
  
  having been colder and wetter than was usual in some regions and slowed  
  
  
  

虽然可以选出正确选项 但是答案里有个解释不是特备明白 A和E里的was ”The insertion of was is unnecessary and misleading"
解释的意思是那样就是缺少连接词的完整句子了吗？unnecessary可以理解 misleading呢？ 查了一下 没有用than was usual 都是than usual 但还是想知道am i on the right track?