What does stockholders' equity represent?

Multiple choice question.

A claim against all of the firm's assets

A residual claim against the firm's liabilities $($The book value of the firm's assets less the book value of its current assets.$)$

A fixed claim against the firm's liabilities

A residual claim against the book value of the firm's assets. $($The book value of the firm's assets less the book value of its liabilities.$)$