Kira Sigard, CFA and an attorney with an investment banking firm, structures a client’s bond issue to include a "poison put". This is a provision that requires the issuer to redeem the bond at par in the case of a corporate takeover, a merger, or anti-takeover measure that would dissipate significant corporate assets. An investor who purchases this bond is protected from what type of risk（）

A. Call Risk.

B. Reinvestment Risk.

C. Event Risk.

简述DK-1型电空制动机紧急阀的组成。