They author's attitude towards the current situation in the exploitation of natural resources is ______.

A．We need to take some measures to protect space.
B．We must preserve good living conditions for both birds and land animals.
C．Our living space should be measured in cubic volume.
D．Our living space on the earth is getting smaller and smaller.

A．the importance of the proper use of land
B．the interdependence of water, soil, and living things
C．the value of the beauty of nature
D．the harmfulness of soil destruction and river floods