Answer:
A. Location
Step-by-step explanation:
A black hole is a massive structure in the space from which light cannot escape. Therefore, the depth of the black hole (B), the speed (C), and size (D) are extremely difficult to measure. However, scientists have been able to locate the position of black holes via the movement of stars and gases around it. Typically, since black holes are extremely dense objects, masses spins around the black holes and form a structure called an accretion disk. By looking at the speed of stars, the scientists can detect where the black holes are in the space.