Mum，you really need to have a rest！You ________in the kitchen ever since you came back home three hours ago.

A．had worked

B．were working

C．have been working

D．worked

下列赋值语句中错误的是

A．float f=11.1f；

B．double d=5.3E12；

C．char c='\r'；

D．byte bb=433；