Answer:
Option B, flagellum
Step-by-step explanation:
Flagellum is a locomotory organ in Euglena that allows it to move through the water. A flagellum is located on the front or anterior side of body of euglena. It looks like a thread like structure which is capable to act like a motor.
Euglena can whip it flagella just like a helicopter propeller and thus it comes under the species category of "species with falgellatory locomotion"
Hence, option B is correct