Describe the overall trend in corn yield from 1988 to 2008. How does the trend in corn yield during the time compare to tends for total nutrients and nitrogen?

The trend in the corn productivity shows an increase from the year 1988 to 2008.

This is because of high yielding varieties of corn, new technology and application of optimum dose of fertilizer and other agronomic activities. The trend in corn yield for the nutrients and nitrogen increases because new high yielding varieties needs more nitrogen as well as other nutrients as compared to local or old varieties so it is concluded that productivity and nutrients uptake increase with the passage of time.

link

it's c. (to reduce the greenhouse effect/carbon gasses)