求问一道OG题目的句子结构，谢谢

Helmet_007

Thai village crafts, as with other cultures, have developed through the principle that form follows function and incorporate readily available materials fashioned using traditional skills.

• A
  
  as with
  
  
  
• B
  
  as did those of
  
  
  
• C
  
  as they have in
  
  
  
• D
  
  like in
  
  
  
• E
  
  like those of
  
  
  

• 请问form follows function and incorporate readily available……的主语是不是principle？如果是principle的话为什么谓语是复数形式？