Who is that?( )Mary A it's B she's C that's

Who is that?( )Mary A it's B she's C that's
Who is that?( )Mary A it's B she's C that's

Who is that?( )Mary A it's B she's C that's
原句翻译成汉语为：那是谁?（是）玛丽.
解析：当我们不知道其性别是,我们要用It来指代这个“未知”的她/他.所以此题我们要选择A