piece,grain,drop:attaches,is attached,attach Invented in 1969,RFID chips are about the size of a ______of sand.Each chip has a unique ID number and ______ to the product.
piece,grain,drop:attaches,is attached,attach Invented in 1969,RFID chips are about the size of a ______of sand.Each chip has a unique ID number and ______ to the product. 【正确答案】：grain; is attached
