a question about reading 24 online class question, reading, online, about, style

zza1700454

From Economics Reading 24's online class,

11.    If money supply and demand are in equilibrium and the central bank sells securities in the open market 

A bank reserves will increase  

B short term interest rate will increase

C firms and households will sell securities for cash.

Why the answer is C? I think it should be B.

Thanks