S7. Students of different abilities are placed together in a cooperative learning groups in that________.

A．Preparing her seminar.
B．Preparing her negotiation.
C．Preparing her arguments.
D．Preparing her show.

A．There are too many underdeveloped countries in the world.
B．Underdeveloped countries have low level of industrial development.
C．Different governments have different views on the question.
D．Even developed countries have complex problems.