Susan is ______ as an "addlehead"—she always leaves her keys on the door.A．who is knownB．w

Susan is ______ as an "addlehead"—she always leaves her keys on the door.

A．who is known

B．which is known

C．whom is known

D．what is known

请帮忙给出正确答案和分析，谢谢！