In "My Last Duchess" all of the following are true except:

A. The Duke lacks a conscience
B. The Duke believes the Duchess was unfaithful
C. The Duchess was most likely murdered by her jealous lover
D. The Duchess was a lively, outgoing woman

C. The Duchess was most likely murdered by her jealous lover

This statement is not explicitly stated in the poem. The Duke only mentions that he had her "put to death". The exact circumstances surrounding the Duchess's death are left ambiguous.