Before us lies the biggest room, _____ with things like guns, dolls and old clothes.

A．filling

B．filled

C．being filled

D．having been filled

pK_a与pH的差值以数学值增减时，药物的离子型与非离子型浓度比值的变化为（）

A.平方根

B.对数值

C.指数值

D.数学值

E.乘方值