In August 1977, a satellite _______ to gather data about the 10 million black holes which are thought to be in the Milky Way.
A.launched B.was launched C.has been launched D.is launched正确答案B
In August 1977, a satellite _______ to gather data about the 10 million black holes which are thought to be in the Milky Way.
A.launched B.was launched C.has been launched D.is launched正确答案B
