Answer:
D. rightward shift in the current supply of soybeans.
Explanation:
A shift in the supply curve is caused when factors other than price either increase the supply of a good (a shift to the right), or decrease the supply of the good (a shift to the left).
In this case, a factor other than price, the expectations of farmers (they are expectations because the lower prices have not materialized) has increased the supply of soybeans, causing a rightward shift of the supply curve of that good.