21.  The comparison is a natural one.

22.  The deal is a natural one for both companies.

23.  The Industrial Revolution was beginning to change the man-made world and science was rapidly transforming the understanding of the natural one.

24.  The natural ones include changes in solar radiation, and sulfate droplets called aerosols cast aloft by erupting volcanoes, which cool the atmosphere by reflecting sunlight.

25.  The report found that substitute wetlands built in exchange for filling in natural ones often lack those important functions.

26.  They have been able to get only one unnatural protein building block at a time substituted for a natural one.

27.  They must have figured that they would need to look natural carrying one, so they worked at it from an early age.

28.  Think of your urge to thin them as a natural one and indulge it.

29.  Until last year, Soviet officials maintained the outbreak was a natural one originating in contaminated meat.

30.  Even if the government is not directly responsible, South Korea traditionally holds it accountable for all disasters, even natural ones.