Billy is a descendant of the earl of lancaster

The sentence above is a simple sentence.

Explanation

The sentence above is a simple sentence because it contains only one independent clause. Simple sentences have no dependent clauses. Moreover, they are also called clausal sentences and they may have modifiers besides a subject, a verb, and an object. On the contrary, compound sentences join two or more independent clauses with a coordinator such as for, and, but, or a semi-colon.

what is the question ?

reflexive.the third one.