How can astronomers "weigh" the supermassive black hole at the center of the milky way? a. by measuring the velocity and orbital radius of stars and other matter orbiting it b. by how much mass it sucks in during a given period c. with the cosmic distance ladder d. by the intensity of its radiation

a) By measuring the velocity and orbital radius of stars and other matter orbiting it

Explanation:

The heavier the mass of the black hole the more matter it will pull because of its gravitational force. So if the black hole is heavy it will pull on stars in the vicinity. When this pull occurs according to the mass of the black hole the velocity of pulling will vary. The higher the mass the higher the velocity.