Article in English: Fresh cabbage can be identified by its crisp leaves. The leaves should be tightly packed for round varieties and only slightly loose for long varieties. Additionally, there should be no signs of browning and the stem should look fresh rather than dry.  Green cabbage is a round variety. Its leaves should be tightly packed together and dark green on the outside. The inner leaves will be a pale green. Red cabbage is another round variety, and its leaves should also be tightly packed together. The outer leaves are especially tough, and all of the leaves should have a reddish purple color. Savoy cabbage is a round variety, but its leaves are crinkled and fairly loose when compared to green and red cabbages. The leaves can range in color from dark green to light green. Napa cabbage is tall and skinny, with loose, pale green leaves. Use a sharp, stainless steel cooking knife with a smooth, sturdy blade. Only use stainless steel knives. Do not use knives made from other metals, because the natural chemicals within the cabbage can react with other metals. As a result, both the cabbage and knife can turn black. Spread a moist paper towel in between the cutting board and the counter to prevent the cutting board from sliding around.  Soak the paper towel in water and squeeze out the excess moisture. This gives the towel just enough tension to prevent it and the cutting board from sliding around.     Do not let the towel stay soaked, though, since a soaked paper towel will be too slippery.     Note that this may not be necessary if you are using a no-slip silicone cutting mat.    Make sure that your hands, the knife, and the cutting board are all clean before you begin.  Use warm water and soap to clean your hands and all the supplies used for cutting the cabbage.     Rinse the knife and cutting board with clean, running water to remove all soapy residue. Wipe dry with clean, dry paper towels.     Do not clean the cabbage yet. The cabbage should be rinsed after you cut it, not beforehand.

Summary in Chinese:
选择卷心菜的新鲜菜头。 用不锈钢刀。 保持砧板稳定。 清洁你做菜的地方和做菜用品，要先确保你的手、不锈钢刀和砧板都是干净的，然后再开始。