Article in English: Not all pens that have a ball are actual "ballpoint" pens, and different pens use different kinds of ink that must be removed in different ways.  Traditional ballpoint pens (like the ubiquitous Bic and Paper Mate) use a fast-drying, oil-based ink that requires a solvent to remove. Rollerball pens, on the other hand, (common manufacturers include Uni-Ball and Pilot), use water-based inks that are fairly easy to remove, while gel pens use a highly-pigmented type of ink that can be a bit more difficult.  If you have the offending pen, go to the website of any online office supply store and search for the name/model of the pen.  The product description will tell you if it is a ballpoint, rollerball, or gel pen. You can also check the pen manufacturer's website for more information, and product-specific ink-removal instructions. If you do not have the pen and don't know what kind it was, first try the method for removing ballpoint ink. If that doesn't work, move on to the method for rollerball ink, and finally, the method for gel ink.  Rinse the garment thoroughly between each treatment, but do not put it in the dryer until the stain is gone! If your garment is machine-washable, as most cotton garments are, you should be safe treating your stain at home.  If your garment is dry-clean or hand-wash only, you are better off taking it to your neighborhood dry-cleaner for assistance.  The cost to have a shirt laundered is usually under $5, and you will save a lot of time and hassle. Be sure to tell the dry cleaner what kind of pen caused the stain, or better yet, put the pen in a plastic bag to prevent further staining, and bring it with you.

Summary in Chinese:
确认要清除的是哪一种墨渍。 清除不明墨水造成的污渍。 查看衣服上的织物标签。