According to the Placarding and Marking for Road Transportation Vehicles of Dangerous Goods (GB 13392-2005), what are the standard dimensions for diamond hazard warning placards (标志牌) mounted on the sides and rear of dangerous goods transport vehicles?

1. 250 mm × 250 mm
2. 100 mm × 100 mm
3. 500 mm × 500 mm
4. 1,000 mm × 1,000 mm