The passage suggests that the present-day problem with regard to computers is ______.

A．To look back to the early days of this passage.
B．To explain what technical problems may occur with computers.
C．To discourage unnecessary investment in computers.
D．To warn against a mentally lazy attitude towards computers.

A．be reasonably doubtful about them
B．check all their answers
C．substitute them for basic thinking
D．use them for business purposes only