In the passage the term "human problems" or "world problems" refers mainly to ______.

A．The environment crisis will not be solved unless we stop using virgin materials.
B．In scientific research, a higher priority should be given to understanding all living systems.
C．Exploration of outer space will finally lead to an improvement on human living conditions.
D．U.S. high-technology companies are applauding this new twist in scientific research.

A．existing products be improved
B．more complex machines and electronic equipment be designed
C．ways to be found to produce better goods using fewer raw materials
D．any new invention and innovation be encouraged in technology