In the Context of Corporations,what Is a White Knight

In the context of corporations,what is a white knight?

A) A more acceptable firm that is willing to acquire the firm threatened by a hostile takeover
B) An attempt to fend off a hostile takeover by selling stock at prices below the market value
C) An attempt to fend off a hostile takeover by requiring the deal to be approved by a majority of shareholders
D) An attempt to fend off a hostile takeover by raising capital through an initial public offering
E) A group of investors who have borrowed money to acquire a firm