20.The commission has directed advertisers to restrict the use of the word natural to foods that do not contain color or flavor additives, chemical preservatives, or nothing that has been synthesized.

A. or nothing that has been

B. or that has been

C. and nothing that is

D. or anything that has been

E. and anything

21. Thai village crafts,as with other cultures,have developed through the principle that follows function and incorporate readily available materials fashioned using traditional skills.

A. as with

B as did those of

C as they have in

D.like in

E. like those of

23. Discussion of greenhouse effect have usually had as a focus the possibility of Earth growing water and to what extent it might, but climatologists have indicated all along that precipitation,storminess,and temperature extremes are likely to have the greatest impact on people.