Which row correctly identifies the mechanism type for each of these two reactions? C$_2$H$_5$Br + KCN CH$_3$COCH$_3$ + HCN
- Aelectrophilic substitution; electrophilic addition
- Belectrophilic substitution; nucleophilic addition
- Cnucleophilic substitution; electrophilic addition
- Dnucleophilic substitution; nucleophilic addition