Not a muscle of the tongue: (A) Genioglossus, (B) Sternohyoid, (C) Hyoglossus, (D) Styloglossus
Answer is B. Intrinsic muscles of the tongue: 

Muscles found entirely within the tongue
Longitudinal, transverse, and vertical muscles
Function - change the shape of the tongue.

Extrinsic muscles of the tongue:

Genioglossus, Styloglossus, and hyoglossus, Palatoglosus.
All insert into the tongue, originate from surrounding structures