Question 3 .
When Albert Einstein developed his general theory of relativity in 1915, he noticed that one of the theory's consequences was that there could be objects that were so massive that nothing, not even light, could escape their gravitational fields.
At first, Einstein found this prediction so strange that he did not believe it. However, later investigations proved that such objects do exist. Today, these objects are known as
A. quasars
B. neutron stars
C. supernovae
D. black holes