Answer:
a) Sagittarius
Step-by-step explanation:
The galactic center of our galaxy is in the direction of the Sagittarius constellation.
There are some things that indicate that a supermassive black hole can be at the center of our galaxy (as well as in the center of many others), the signs are powerful radio waves coming from the center of the galaxy.
So this source of radio waves being in the direction of the Sagittarius constellation is called SagittariusA*.