20．---I got up at five this morning, I thought it was Friday．

---You _____ so early．It is Sunday today; you don’t have to go to work．

A．mustn’t have got up

B．needn’t have got up

C．needn’t get up

D．mustn’t get up

车钩钩舌变形调修后在使用中发生断裂的主要原因之一是加热温度或调修温度达不到规定要求所致。