In order not to be disturbed, I spent three hours _______ in my study.

A．locking

B．locked

C．to lock

D．to be locked

水痘的传染期是

A．发热至痂脱落为止

B．出疹期至痂脱落为止

C．潜伏期至结痂

D．前驱期至出疹

E．自出疹前1～2天至皮疹全部干燥结痂为止