<human>:  How do I remove grass stains from my white shirt?
<bot>: The best way to remove grass stains from a white shirt is to first soak the fabric in cold water for 30 minutes. Then, mix a solution of equal parts white vinegar and laundry detergent, and use a soft brush or sponge to rub the solution into the stain. Rinse the shirt until the stain is gone, then wash it in the washing machine as usual.