A．There is no easy technological solution to it．
B．It will advance nuclear technology．
C．There is no easy way．to understand it．
D．It will do a lot of harm to mankind．

A．The deciding factor in children’s academic performance．
B．The health problems of children raised by a single parent．
C．The relation between children’s self-control and their future success．
D．The reason why New Zealand children seem to have better self-control．

A．Those with a criminal record mostly come from single parent families．
B．Children raised by single parents will have a hard time in their thirties．
C．Parents must learn to exercise self-control in front of their children．
D．Lack of self-control in parents is a disadvantage for their children．