The First, Indirect Detection of Gravitational Waves in the 1970s

The first, indirect detection of gravitational waves in the 1970s involved

A) a pulsar that was in the same star system with a neutron star
B) the black hole in the Cygnus X-1 system
C) a star that was swelling up to be the largest red giant astronomers had ever seen
D) a spacecraft that we purposely sent to fall into the strong gravity of the Sun
E) the collapse of a huge garbage dump in the town of Bayonne, New Jersey