sentence: The pie chart shows the principal causes which explain why agricultural lands become less productive , whereas the table correlates these causes with three different regions of the world which had land degraded , namely North America , Europe and Oceania , during the 1990s .
modified: The pie chart shows the principal causes which justify why agricultural lands became less productive , whereas the table correlates these causes with three different regions of the world which had land degraded , namely North America , Europe and Oceania , during the 1990s .
transformation: VERB, VERB:TENSE