Why Is Supernova 1987A Particularly Important to Astronomers

Why is Supernova 1987A particularly important to astronomers?

A) It provided the first observational evidence that supernovae actually occur.
B) It was the nearest supernova detected in nearly 400 years.
C) It occurred only a few dozen light- years from Earth.
D) It was the first supernova detected in nearly 400 years.
E) It provided the first evidence that neutron stars exist.