Children can learn their mother tongue without being systematically taught.

A．the development of present technologies can not provide any answers to today's problems
B．an increasing number of young scientists are taking a great interest in biological and social sciences
C．many people as well as scientists have come to understand the limits of natural resources
D．many scientists argue that high technology is something but not everything

A．A growing number of Americans are doubtful about what high technology can do in solving the world's problems.
B．Many scientists are beginning to believe that the better understanding of human beings will play a more decisive role in solving the world's problems.
C．More and more young scientists are trying their best to find new ways to solve the world's problems.
D．Technological creativity will still play a very important part in solving the world's problems.