The great scientist became world-known in the early 1970s,__..
The great scientist became world-known in the early 1970s,______ he and another scientist made new discoveries about black holes.A.whichB.whereC.whenD.then
A terrible earthquake happened in that district at the end o..
A terrible earthquake happened in that district at the end of 2004, ____ many countries in the world paid close attention to this. A.whereB.whenC.whichD.what