title: 选择2Sinceyouareverytired,you____f 
desc: Since you are very tir ,you ____finish the work today. 
  
  A don’t need Bneedn’ to Cnot needDneedn’t
  
answer: needn't
  need既可以做情态动词，又可以做行为动词。当做情态动词的时候，否定直接在后面加not，且加动词原形。但当行为动词是，有人称时态的变化。