【Nobody 主语】but doctors or nurses and those invited by Dr Hu_【A_】__ to enter the patient’s room.A.is allowed B.are allowed
nobody/no one+but/except+n(pl)+单数谓语动词.
原句结构可调整为如下,以便于理
Nobody __is allowed___ to enter the patient’s room 【but doctors or nurses and those invited by Dr Hu.】 A.is allowed B.are allowed