One of the Strategies Used by Poxviruses to Inhibit Host $\beta$

One of the strategies used by poxviruses to inhibit host defenses involves the synthesis of a viral serpin.What is the function of the serpin?

A) It inhibits components of the complement system.
B) It prevent the presentation of peptides on MHC-I.
C) It is a soluble receptor for the tumor necrosis factor.
D) It binds to the PKR kinase and inhibits its activity.
E) It inhibits a serine protease that activates interleukin-1 $\beta$ .