Answer:
The correct answer would be The harmless bacteria would not have been transformed, and the mice would have lived.
Transformation of harmless or rough strain of bacteria into a harmful or smooth strain required the transport of genetic material from smooth strain to the rough strain.
DNA (deoxyribonucleic acid) is the genetic material of most of the organisms including bacteria.
Thus, if all the the nucleic acids in the mixture of heat-killed bacteria has been digested before adding the mixture to the harmless bacteria then the harmless bacteria would not have been transformed. Consequently, the mice would have lived.