Choose the word which is different from the rest: Barley, Rice, Wheat, Mustard, Bajra.

All except Mustard are foodgrains, while mustard is an oilseed.  A grain is a small, hard, dry fruit with or without an attached hull layer, harvested for human or animal consumption.
The major U.S. oilseed crops are soybeans, cottonseed, sunflower seed and canola.  Soybeans are the dominant oilseed in the United States, accounting for about 90 percent of U.S. oilseed production.