What might have been discussed in the preceding paragraphs

A．The volume of the atmosphere is four times that of the world's oceans.
B．The water in the oceans is the main source of rain and snow on land areas.
C．The atmosphere is mainly composed of the vapor carried over land by air currents.
D．The earth can not support the water in the atmosphere if it falls down onto the earth suddenly.

A．urge employees to do better in their work
B．tell employee how well they have done
C．gain participation in the process
D．tell employees what they should have done